This was used on a polaris from the factory that has never had work done on the engine. The farm mechanic was having a difficult time fitting the pistons in. Once together the engine was turned over and the piston was hitting. Taking it apart and carefully measuring the pistons were 2.5mm off size of the originals. Unfortunately the packing slips were thrown away, and I can't return it. It appeared of good quality and all parts needed for the job were present, they just werent the size we ordered.