Triumph TR4/4A/5/250 Caliper Pistons & Repair Kits
The imperial threaded calipers fitted to late TR4/5/250/6 were fitted with 2
different types of piston and seal kit. It is possible that your vehicle
may have had alternate calipers fitted at some stage of its life, so it is important
firstly to check that both calipers are the same type and secondly of which type
they are, before ordering any service parts.