Very hard to find original Hepolite Powermax hi-compression .060" oversize piston set to fit all Triumph T140 750 twin models 1973-83. Compression ratio is 10:5-1 They work out to a bore size of roughly 3.050" and may also work in some of the big bore cylinders for 650 twins depending on wrist pin diameter? I will leave the research up to you to decide. These were made by the same English company who made the pistons for the Triumph factory. Very high quality. Not made in Taiwan.