Yes as far as the piston it's self design related but if it's a stock/oem piston depends on the size and the size of your cylinder. My '06 YZ 125 was a C size cylinder so you should run the C piston. When you look in the manual it gives you the clearance spec's of each. wiseco makes one piston size but a couple different models. Vertex I think has a couple different sizes and models.