Piston By Rickard Nebrer
Standard size genuine BSA unit single pistons are not usually marked STD on the top, and the number stamped on the top is often BSA´s works number for the piston,
Standard pistons can be readily identyfied by the letters H, M, L stamped on the top.
These are references for factory selective assembly with similarly marked cylinder barrels, and signify High, Medium, or Low.
No such marks appear on the oversize pistons, but usualy the oversize is stamped on the crown.
© Rickard Nebrér