BSA C10/C11/C11G/C12 250cc Piston +020 = 63,5 mm

Piston Assembly complete
BSA C10/C11/C12 Piston Std.
incl. rings, gudgeon pin, circlips
STD= 63mm   +20 = 63.5 mm
Piston Clearance 0.12mm or 45thou
C11 1939-55
C12 1955-58
can also be used for C10, even if they usually had a flat top