I'm about to get a new piston and the barrol relined. There is 4 pistons avliable all changing by 0.01mm by diaminter(sp). What are the advantages of the different size's?

so you can get the right size piston for you bore if your not re-plating.

I had my barrel replated by the place in Weston-Super-Mare (Langcourts??) about a year ago. I supplied the new piston to them and they plated/honed the barrel to suit. They even charged a bit less than the told me on the phone and think it cost about