ITEM DESCRIPTION: NOS Yamaha Piston, 2nd OS (.50mm). Yamaha Part # YA 6 125cc 56.50. NOTE: This is the hard to find early style which uses regular rings. I have the later style (Keystone rings) in another listing. These cannot be interchanged unless you match the ring style. Fits These Yamaha Models: Yamaha Motorcycle 1965 YA6 CRANK PISTON Yamaha Motorcycle 1966 YA6 CRANK PISTON Yamaha Motorcycle 1966 YA6B CRANK PISTON Yamaha Motorcycle 1964 YA6 CRANK PISTON NOTE: We purchased the entire inventory of an old Yamaha dealer that closed down many years ago. This dealer was in business from the late 1960s until the early 1990s. We have 1000s of NOS and some used parts that will soon be listed . Please DO NOT ASK if I have this or that... the parts have not been inventoried so I have no idea what's out there? Check my store periodically (I will get them as soon as I'm able). Listing and template services provided by inkFrog