heres my story,i bought a set of namura power pistons size 20 over for rebuild.gave my pistons to engine builder to do a few things to them.anyways i get my clyinders bored up for my new pistons only to find out that the shop had to bore one hole larger to match pistons. pistons were stamped the same but it turns out one was somewhat larger than the other great!well now i find out that the rings sent with the pistons wont even fit because the rings are to thick or the ring grooves are to small ethier way they wont work.i cant send pistons back because of modifications that have been made to them so anyways im out for price of the pistons& cost for boring cylinders that wont work with any other set of pistons because of the friggin diff in size.im calling where i bought piston tomorrow to see what might be done but i believe im getting screwed this time.