diff --git a/pySim/filesystem.py b/pySim/filesystem.py
index fe8f591..598121b 100644
--- a/pySim/filesystem.py
+++ b/pySim/filesystem.py
@@ -913,7 +913,7 @@
                         self._cmd.poutput_json(data)
 
     def __init__(self, fid: str, sfid: str = None, name: str = None, desc: str = None,
-                 parent: Optional[CardDF] = None, rec_len={1, None}, **kwargs):
+                 parent: Optional[CardDF] = None, rec_len: Size = (1, None), **kwargs):
         """
         Args:
             fid : File Identifier (4 hex digits)
@@ -921,7 +921,7 @@
             name : Brief name of the file, lik EF_ICCID
             desc : Description of the file
             parent : Parent CardFile object within filesystem hierarchy
-            rec_len : set of {minimum_length, recommended_length}
+            rec_len : Tuple of (minimum_length, recommended_length)
         """
         super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, parent=parent, **kwargs)
         self.rec_len = rec_len
@@ -1044,7 +1044,7 @@
     # we don't really have any special support for those; just recycling LinFixedEF here
 
     def __init__(self, fid: str, sfid: str = None, name: str = None, desc: str = None, parent: CardDF = None,
-                 rec_len={1, None}, **kwargs):
+                 rec_len: Size = (1, None), **kwargs):
         super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, parent=parent, rec_len=rec_len, **kwargs)
 
 
diff --git a/pySim/gsm_r.py b/pySim/gsm_r.py
index ccab87f..8464197 100644
--- a/pySim/gsm_r.py
+++ b/pySim/gsm_r.py
@@ -61,7 +61,7 @@
 
     def __init__(self):
         super().__init__(fid='6ff1', sfid=None, name='EF.EN',
-                         desc='Functional numbers', rec_len={9, 9})
+                         desc='Functional numbers', rec_len=(9, 9))
         self._construct = Struct('functional_number_and_type'/FuncNTypeAdapter(Bytes(8)),
                                  'list_number'/Int8ub)
 
@@ -166,7 +166,7 @@
     """Section 7.5"""
 
     def __init__(self):
-        super().__init__(fid='6ff3', sfid=None, name='EF.CallconfI', rec_len={21, 21},
+        super().__init__(fid='6ff3', sfid=None, name='EF.CallconfI', rec_len=(21, 21),
                          desc='Call Configuration of emergency calls Information')
         self._construct = Struct('t_dur'/Int24ub,
                                  't_relcalc'/Int32ub,
@@ -193,7 +193,7 @@
 
     def __init__(self):
         super().__init__(fid='6ff5', sfid=None, name='EF.GsmrPLMN',
-                         desc='GSM-R network selection', rec_len={9, 9})
+                         desc='GSM-R network selection', rec_len=(9, 9))
         self._construct = Struct('plmn'/BcdAdapter(Bytes(3)),
                                  'class_of_network'/BitStruct('supported'/FlagsEnum(BitsInteger(5), vbs=1, vgcs=2, emlpp=4, fn=8, eirene=16),
                                                               'preference'/BitsInteger(3)),
@@ -207,7 +207,7 @@
 
     def __init__(self):
         super().__init__(fid='6f8d', sfid=None, name='EF.IC',
-                         desc='International Code', rec_len={7, 7})
+                         desc='International Code', rec_len=(7, 7))
         self._construct = Struct('next_table_type'/NextTableType,
                                  'id_of_next_table'/HexAdapter(Bytes(2)),
                                  'ic_decision_value'/BcdAdapter(Bytes(2)),
@@ -219,7 +219,7 @@
 
     def __init__(self):
         super().__init__(fid='6f80', sfid=None, name='EF.NW',
-                         desc='Network Name', rec_len={8, 8})
+                         desc='Network Name', rec_len=(8, 8))
         self._construct = GsmString(8)
 
 
@@ -228,7 +228,7 @@
 
     def __init__(self, fid, name, desc):
         super().__init__(fid=fid, sfid=None,
-                         name=name, desc=desc, rec_len={6, 6})
+                         name=name, desc=desc, rec_len=(6, 6))
         self._construct = Struct('next_table_type'/NextTableType,
                                  'id_of_next_table'/HexAdapter(Bytes(2)),
                                  'decision_value'/BcdAdapter(Bytes(2)),
@@ -240,7 +240,7 @@
 
     def __init__(self, fid, name, desc):
         super().__init__(fid=fid, sfid=None,
-                         name=name, desc=desc, rec_len={3, 3})
+                         name=name, desc=desc, rec_len=(3, 3))
         # header and other records have different structure. WTF !?!
         self._construct = Struct('next_table_type'/NextTableType,
                                  'id_of_next_table'/HexAdapter(Bytes(2)),
diff --git a/pySim/sysmocom_sja2.py b/pySim/sysmocom_sja2.py
index 2edc916..d00a2cb 100644
--- a/pySim/sysmocom_sja2.py
+++ b/pySim/sysmocom_sja2.py
@@ -85,7 +85,7 @@
 
 class EF_0348_KEY(LinFixedEF):
     def __init__(self, fid='6f22', name='EF.0348_KEY', desc='TS 03.48 OTA Keys'):
-        super().__init__(fid, name=name, desc=desc, rec_len={27, 35})
+        super().__init__(fid, name=name, desc=desc, rec_len=(27, 35))
 
     def _decode_record_bin(self, raw_bin_data):
         u = unpack('!BBB', raw_bin_data[0:3])
@@ -103,7 +103,7 @@
 
 class EF_0348_COUNT(LinFixedEF):
     def __init__(self, fid='6f23', name='EF.0348_COUNT', desc='TS 03.48 OTA Counters'):
-        super().__init__(fid, name=name, desc=desc, rec_len={7, 7})
+        super().__init__(fid, name=name, desc=desc, rec_len=(7, 7))
 
     def _decode_record_bin(self, raw_bin_data):
         u = unpack('!BB5s', raw_bin_data)
@@ -118,7 +118,7 @@
 
 class EF_GP_COUNT(LinFixedEF):
     def __init__(self, fid='6f26', name='EF.GP_COUNT', desc='GP SCP02 Counters'):
-        super().__init__(fid, name=name, desc=desc, rec_len={5, 5})
+        super().__init__(fid, name=name, desc=desc, rec_len=(5, 5))
 
     def _decode_record_bin(self, raw_bin_data):
         u = unpack('!BBHB', raw_bin_data)
@@ -127,7 +127,7 @@
 
 class EF_GP_DIV_DATA(LinFixedEF):
     def __init__(self, fid='6f27', name='EF.GP_DIV_DATA', desc='GP SCP02 key diversification data'):
-        super().__init__(fid, name=name, desc=desc, rec_len={12, 12})
+        super().__init__(fid, name=name, desc=desc, rec_len=(12, 12))
 
     def _decode_record_bin(self, raw_bin_data):
         u = unpack('!BB8s', raw_bin_data)
@@ -241,7 +241,7 @@
 class EF_GBA_INT_KEY(LinFixedEF):
     def __init__(self, fid='af33', name='EF.GBA_INT_KEY'):
         super().__init__(fid, name=name,
-                         desc='Secret key for GBA key derivation', rec_len={32, 32})
+                         desc='Secret key for GBA key derivation', rec_len=(32, 32))
         self._construct = GreedyBytes
 
 
diff --git a/pySim/ts_102_221.py b/pySim/ts_102_221.py
index 6e04e96..83ddb85 100644
--- a/pySim/ts_102_221.py
+++ b/pySim/ts_102_221.py
@@ -588,7 +588,7 @@
         pass
 
     def __init__(self, fid='2f00', sfid=0x1e, name='EF.DIR', desc='Application Directory'):
-        super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len={5, 54})
+        super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=(5, 54))
         self._tlv = EF_DIR.ApplicationTemplate
 
 # TS 102 221 Section 13.2
diff --git a/pySim/ts_31_102.py b/pySim/ts_31_102.py
index b8a33e7..5df7369 100644
--- a/pySim/ts_31_102.py
+++ b/pySim/ts_31_102.py
@@ -333,7 +333,7 @@
                                            IdsOfSelectedEpsAlgos]):
         pass
 
-    def __init__(self, fid="4f03", sfid=0x03, name='EF.5GS3GPPNSC', rec_len={57, None},
+    def __init__(self, fid="4f03", sfid=0x03, name='EF.5GS3GPPNSC', rec_len=(57, None),
                  desc='5GS 3GPP Access NAS Security Context', **kwargs):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._tlv = EF_5GS3GPPNSC.FiveGSNasSecurityContext
@@ -597,7 +597,7 @@
 
     def __init__(self, fid='6fb7', sfid=0x01, name='EF.ECC',
                  desc='Emergency Call Codes'):
-        super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len={4, 20})
+        super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=(4, 20))
 
     def _decode_record_bin(self, in_bin):
         # mandatory parts
@@ -661,7 +661,7 @@
 
 # TS 31.102 Section 4.2.33
 class EF_ICI(CyclicEF):
-    def __init__(self, fid='6f80', sfid=0x14, name='EF.ICI', rec_len={28, 48},
+    def __init__(self, fid='6f80', sfid=0x14, name='EF.ICI', rec_len=(28, 48),
                  desc='Incoming Call Information', **kwargs):
         super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._construct = Struct('alpha_id'/HexAdapter(Bytes(this._.total_len-28)),
@@ -677,7 +677,7 @@
 
 # TS 31.102 Section 4.2.34
 class EF_OCI(CyclicEF):
-    def __init__(self, fid='6f81', sfid=0x15, name='EF.OCI', rec_len={27, 47},
+    def __init__(self, fid='6f81', sfid=0x15, name='EF.OCI', rec_len=(27, 47),
                  desc='Outgoing Call Information', **kwargs):
         super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._construct = Struct('alpha_id'/HexAdapter(Bytes(this._.total_len-27)),
@@ -692,7 +692,7 @@
 
 # TS 31.102 Section 4.2.35
 class EF_ICT(CyclicEF):
-    def __init__(self, fid='6f82', sfid=None, name='EF.ICT', rec_len={3, 3},
+    def __init__(self, fid='6f82', sfid=None, name='EF.ICT', rec_len=(3, 3),
                  desc='Incoming Call Timer', **kwargs):
         super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._construct = Struct('accumulated_call_timer'/Int24ub)
@@ -700,7 +700,7 @@
 # TS 31.102 Section 4.2.38
 class EF_CCP2(LinFixedEF):
     def __init__(self, fid='6f4f', sfid=0x16, name='EF.CCP2', desc='Capability Configuration Parameters 2', **kwargs):
-        super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len={15, None}, **kwargs)
+        super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len=(15, None), **kwargs)
 
 # TS 31.102 Section 4.2.47
 class EF_EST(EF_UServiceTable):
@@ -769,7 +769,7 @@
 # TS 31.102 Section 4.2.80
 class EF_MSK(LinFixedEF):
     def __init__(self, fid='6fd7', sfid=None, name='EF.MSK', desc='MBMS Service Key List', **kwargs):
-        super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len={20, None}, **kwargs)
+        super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len=(20, None), **kwargs)
         msk_ts_constr = Struct('msk_id'/Int32ub, 'timestamp_counter'/Int32ub)
         self._construct = Struct('key_domain_id'/HexAdapter(Bytes(3)),
                                  'num_msk_id'/Int8ub,
@@ -792,7 +792,7 @@
         pass
 
     def __init__(self, fid='6fd8', sfid=None, name='EF.MUK', desc='MBMS User Key', **kwargs):
-        super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len={None, None}, **kwargs)
+        super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len=(None, None), **kwargs)
         self._tlv = EF_MUK.EF_MUK_Collection
 
 # TS 31.102 Section 4.2.83
@@ -807,7 +807,7 @@
         pass
 
     def __init__(self, fid='6fda', sfid=None, name='EF.GBANL', desc='GBA NAF List', **kwargs):
-        super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len={None, None}, **kwargs)
+        super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len=(None, None), **kwargs)
         self._tlv = EF_GBANL.EF_GBANL_Collection
 
 # TS 31.102 Section 4.2.85
@@ -822,7 +822,7 @@
 class EF_NAFKCA(LinFixedEF):
     class NAF_KeyCentreAddress(BER_TLV_IE, tag=0x80):
         _construct = HexAdapter(GreedyBytes)
-    def __init__(self, fid='6fdd', sfid=None, name='EF.NAFKCA', rec_len={None, None},
+    def __init__(self, fid='6fdd', sfid=None, name='EF.NAFKCA', rec_len=(None, None),
                  desc='NAF Key Centre Address', **kwargs):
         super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._tlv = EF_NAFKCA.NAF_KeyCentreAddress
@@ -853,7 +853,7 @@
     class EF_NCP_IP_Collection(TLV_IE_Collection,
                                nested=[AccessPointName, Login, Password, BearerDescription]):
         pass
-    def __init__(self, fid='6fe2', sfid=None, name='EF.NCP-IP', rec_len={None, None},
+    def __init__(self, fid='6fe2', sfid=None, name='EF.NCP-IP', rec_len=(None, None),
                  desc='Network Connectivity Parameters for USIM IP connections', **kwargs):
         super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._tlv = EF_NCP_IP.EF_NCP_IP_Collection
@@ -890,7 +890,7 @@
                                    nested=[KSI_ASME, K_ASME, UplinkNASCount, DownlinkNASCount,
                                            IDofNASAlgorithms]):
         pass
-    def __init__(self, fid='6fe4', sfid=0x18, name='EF.EPSNSC', rec_len={54, 128},
+    def __init__(self, fid='6fe4', sfid=0x18, name='EF.EPSNSC', rec_len=(54, 128),
                  desc='EPS NAS Security Context', **kwargs):
         super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._tlv = EF_EPSNSC.EPS_NAS_Security_Context
@@ -905,7 +905,7 @@
 
 # TS 31.102 Section 4.2.101
 class EF_IPS(CyclicEF):
-    def __init__(self, fid='6ff1', sfid=None, name='EF.IPS', rec_len={4, 4},
+    def __init__(self, fid='6ff1', sfid=None, name='EF.IPS', rec_len=(4, 4),
                  desc='IMEI(SV) Pairing Status', **kwargs):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._construct = Struct('status'/PaddedString(2, 'ascii'),
@@ -975,7 +975,7 @@
 # TS 31.102 Section 4.4.11.9
 class EF_OPL5G(LinFixedEF):
     def __init__(self, fid='6f08', sfid=0x08, name='EF.OPL5G', desc='5GS Operator PLMN List', **kwargs):
-        super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len={10, None}, **kwargs)
+        super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len=(10, None), **kwargs)
         Tai = Struct('mcc_mnc'/BcdAdapter(Bytes(3)), 'tac_min'/HexAdapter(Bytes(3)),
                      'tac_max'/HexAdapter(Bytes(3)))
         self._construct = Struct('tai'/Tai, 'pnn_record_id'/Int8ub)
@@ -1131,7 +1131,7 @@
             EF_ACMmax(service=13),
             EF_UST(),
             CyclicEF('6f39', None, 'EF.ACM',
-                     'Accumulated call meter', rec_len={3, 3}, service=13),
+                     'Accumulated call meter', rec_len=(3, 3), service=13),
             TransparentEF('6f3e', None, 'EF.GID1', 'Group Identifier Level 1', service=17),
             TransparentEF('6f3f', None, 'EF.GID2', 'Group Identifier Level 2', service=18),
             EF_SPN(service=19),
diff --git a/pySim/ts_51_011.py b/pySim/ts_51_011.py
index 68b32ce..d16ea72 100644
--- a/pySim/ts_51_011.py
+++ b/pySim/ts_51_011.py
@@ -343,7 +343,7 @@
 # TS 51.011 Section 10.5.1
 class EF_ADN(LinFixedEF):
     def __init__(self, fid='6f3a', sfid=None, name='EF.ADN', desc='Abbreviated Dialing Numbers', **kwargs):
-        super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len={14, 30}, **kwargs)
+        super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=(14, 30), **kwargs)
         self._construct = Struct('alpha_id'/COptional(GsmStringAdapter(Rpad(Bytes(this._.total_len-14)), codec='ascii')),
                                  'len_of_bcd'/Int8ub,
                                  'ton_npi'/TonNpi,
@@ -354,7 +354,7 @@
 # TS 51.011 Section 10.5.5
 class EF_SMS(LinFixedEF):
     def __init__(self, fid='6f3c', sfid=None, name='EF.SMS', desc='Short messages', **kwargs):
-        super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len={176, 176}, **kwargs)
+        super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=(176, 176), **kwargs)
 
     def _decode_record_bin(self, raw_bin_data):
         def decode_status(status):
@@ -385,7 +385,7 @@
 # TS 51.011 Section 10.5.5
 class EF_MSISDN(LinFixedEF):
     def __init__(self, fid='6f40', sfid=None, name='EF.MSISDN', desc='MSISDN', **kwargs):
-        super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len={15, 34}, **kwargs)
+        super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=(15, 34), **kwargs)
 
     def _decode_record_hex(self, raw_hex_data):
         return {'msisdn': dec_msisdn(raw_hex_data)}
@@ -427,7 +427,7 @@
                 raise ValueError
 
     def __init__(self, fid='6f42', sfid=None, name='EF.SMSP', desc='Short message service parameters', **kwargs):
-        super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len={28, None}, **kwargs)
+        super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=(28, None), **kwargs)
         ScAddr = Struct('length'/Int8ub, 'ton_npi'/TonNpi, 'call_number'/BcdAdapter(Rpad(Bytes(10))))
         self._construct = Struct('alpha_id'/COptional(GsmStringAdapter(Rpad(Bytes(this._.total_len-28)))),
                                  'parameter_indicators'/InvertAdapter(FlagsEnum(Byte, tp_dest_addr=1, tp_sc_addr=2,
@@ -455,21 +455,21 @@
 
 # TS 51.011 Section 10.5.8
 class EF_SMSR(LinFixedEF):
-    def __init__(self, fid='6f47', sfid=None, name='EF.SMSR', desc='SMS status reports', rec_len={30, 30}, **kwargs):
+    def __init__(self, fid='6f47', sfid=None, name='EF.SMSR', desc='SMS status reports', rec_len=(30, 30), **kwargs):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._construct = Struct(
             'sms_record_id'/Int8ub, 'sms_status_report'/HexAdapter(Bytes(29)))
 
 
 class EF_EXT(LinFixedEF):
-    def __init__(self, fid, sfid=None, name='EF.EXT', desc='Extension', rec_len={13, 13}, **kwargs):
+    def __init__(self, fid, sfid=None, name='EF.EXT', desc='Extension', rec_len=(13, 13), **kwargs):
         super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._construct = Struct(
             'record_type'/Int8ub, 'extension_data'/HexAdapter(Bytes(11)), 'identifier'/Int8ub)
 
 # TS 51.011 Section 10.5.16
 class EF_CMI(LinFixedEF):
-    def __init__(self, fid='6f58', sfid=None, name='EF.CMI', rec_len={2, 21},
+    def __init__(self, fid='6f58', sfid=None, name='EF.CMI', rec_len=(2, 21),
                  desc='Comparison Method Information', **kwargs):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._construct = Struct(
@@ -484,9 +484,9 @@
             EF_ADN(fid='6f3b', name='EF.FDN', desc='Fixed dialling numbers'),
             EF_SMS(),
             LinFixedEF(fid='6f3d', name='EF.CCP',
-                       desc='Capability Configuration Parameters', rec_len={14, 14}),
+                       desc='Capability Configuration Parameters', rec_len=(14, 14)),
             LinFixedEF(fid='6f4f', name='EF.ECCP',
-                       desc='Extended Capability Configuration Parameters', rec_len={15, 32}),
+                       desc='Extended Capability Configuration Parameters', rec_len=(15, 32)),
             EF_MSISDN(),
             EF_SMSP(),
             EF_SMSS(),
@@ -790,7 +790,7 @@
 
 # TS 51.011 Section 10.3.31
 class EF_NIA(LinFixedEF):
-    def __init__(self, fid='6f51', sfid=None, name='EF.NIA', rec_len={1, 32},
+    def __init__(self, fid='6f51', sfid=None, name='EF.NIA', rec_len=(1, 32),
                  desc='Network\'s Indication of Alerting', **kwargs):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._construct = Struct(
@@ -895,21 +895,21 @@
 
 # TS 51.011 Section 10.3.42
 class EF_OPL(LinFixedEF):
-    def __init__(self, fid='6fc6', sfid=None, name='EF.OPL', rec_len={8, 8}, desc='Operator PLMN List', **kwargs):
+    def __init__(self, fid='6fc6', sfid=None, name='EF.OPL', rec_len=(8, 8), desc='Operator PLMN List', **kwargs):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._construct = Struct('lai'/Struct('mcc_mnc'/BcdAdapter(Bytes(3)),
                                  'lac_min'/HexAdapter(Bytes(2)), 'lac_max'/HexAdapter(Bytes(2))), 'pnn_record_id'/Int8ub)
 
 # TS 51.011 Section 10.3.44 + TS 31.102 4.2.62
 class EF_MBI(LinFixedEF):
-    def __init__(self, fid='6fc9', sfid=None, name='EF.MBI', rec_len={4, 5}, desc='Mailbox Identifier', **kwargs):
+    def __init__(self, fid='6fc9', sfid=None, name='EF.MBI', rec_len=(4, 5), desc='Mailbox Identifier', **kwargs):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._construct = Struct('mbi_voicemail'/Int8ub, 'mbi_fax'/Int8ub, 'mbi_email'/Int8ub,
                                  'mbi_other'/Int8ub, 'mbi_videocall'/COptional(Int8ub))
 
 # TS 51.011 Section 10.3.45 + TS 31.102 4.2.63
 class EF_MWIS(LinFixedEF):
-    def __init__(self, fid='6fca', sfid=None, name='EF.MWIS', rec_len={5, 6},
+    def __init__(self, fid='6fca', sfid=None, name='EF.MWIS', rec_len=(5, 6),
                  desc='Message Waiting Indication Status', **kwargs):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._construct = Struct('mwi_status'/FlagsEnum(Byte, voicemail=1, fax=2, email=4, other=8, videomail=16),
@@ -932,7 +932,7 @@
 
 # TS 51.011 Section 10.3.51
 class EF_MMSN(LinFixedEF):
-    def __init__(self, fid='6fce', sfid=None, name='EF.MMSN', rec_len={4, 20}, desc='MMS Notification', **kwargs):
+    def __init__(self, fid='6fce', sfid=None, name='EF.MMSN', rec_len=(4, 20), desc='MMS Notification', **kwargs):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._construct = Struct('mms_status'/HexAdapter(Bytes(2)), 'mms_implementation'/HexAdapter(Bytes(1)),
                                  'mms_notification'/HexAdapter(Bytes(this._.total_len-4)), 'ext_record_nr'/Byte)
@@ -974,7 +974,7 @@
     class MMS_User_Preferences(TLV_IE_Collection,
                                nested=[MMS_Implementation, MMS_UserPref_ProfileName, MMS_UserPref_Info]):
         pass
-    def __init__(self, fid='6fd1', sfid=None, name='EF.MMSUP', rec_len={1, None},
+    def __init__(self, fid='6fd1', sfid=None, name='EF.MMSUP', rec_len=(1, None),
                  desc='MMS User Preferences', **kwargs):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len, **kwargs)
         self._tlv = EF_MMSUP.MMS_User_Preferences
@@ -1000,7 +1000,7 @@
             EF_ServiceTable('6f38', None, 'EF.SST',
                             'SIM service table', table=EF_SST_map, size=(2, 16)),
             CyclicEF('6f39', None, 'EF.ACM',
-                     'Accumulated call meter', rec_len={3, 3}),
+                     'Accumulated call meter', rec_len=(3, 3)),
             TransparentEF('6f3e', None, 'EF.GID1', 'Group Identifier Level 1'),
             TransparentEF('6f3f', None, 'EF.GID2', 'Group Identifier Level 2'),
             EF_SPN(),