This is a aftermarket  top overhaul kit featuring 2 new pistons, oem style w/dual rings, pins, circlips , full major overhaul gasket w/ crank seals  kit as shown. This set exceeds the MFGs specs , Designed to replace the oem elkos in all respects.

Smoother running due to better balance, stonger and better heat transfer. We run em in our trikes and use them in our shop for the past 10+ years

This is set is for 72.50 std bore  503  rotax. .50mm oversize .020"