Stuart, The service kit for disc callipers consists of 1 rubber seal that goes in the cylinder, the rubber flange that goes around the piston and a spring clip. these items prevent the piston from getting moisture and grit in it which in turn leads to sticky brakes etc... Once I have found a good supplier of the kits anyone who suffers from sticky brakes or who is looking at changing their callipers for whatever reason should try servicing the calliper and install the new components. It is very rare that a calliper is actually knackered to the point of requiring replacement. I think I can actually get them from the cortina owners club. Rgds James RG