Fits all model 200cc Bultacos. Some models may need the piston to be modified. Be sure to tell us what model you are fitting the piston to, and we will do the modification here before shipping off to you. However, these pistons fit many models as they are without modifications. Standard bore on the 200cc models is 64.50mm & oversizes will be available up to 66.50mm in 1/2mm increments.