Most minis up to 1974 had the 25D type distributor fitted with side or top entry caps. This rotor arm fits both but for any sort of performance use they have failed because the contact blade on the arm is now riveted and becomes loose, so for peace of mind use GRA101.
If you have an original 25D type distributor this is an upgraded arm (blade moulded and riveted )for performance use because the only other type available now are likely to fail at high revs. The blade because it is thin and not moulded in becomes loose at the rivet and shudders causing electric engine failure.
Top-entry cap takes plug-in wires and will interchange with GDC102. This is an alternative for side entry cap GDC102 which some believe is less prone to wet-weather problems. Features aluminium contacts.
This is the original mini distributor cap where the leads were secured by screws and was fitted to the 25D range of lucas distributors. This cap had side entry leads and is now only available from one or two manufactures owing to its rarity.GDC103 is straight forward replacement but with push in leads and was better in wet weather conditions