Stock and oversized pistons are alot cheaper. This piston is alot bigger then the 50mm stock bore and guess that is why. I am not paying that. I will probably have it bored to 54mm and use the 4th oversized xr100 piston or find new cylinder. Still have to price xr piston to decide. If it is still tomuch I might just redu topend of 110 engine I have and stick it in there. Probably should anyway but kinda wanted to keep the 90 a 90.