I am doing my top end and bought a vertex piston for my ktm250sx. For the life of me I couldn't get the circlips in the piston. It seemed like they were way too big and had too much spring to them. I finally got one in and it didn't look like it was seated very well in the grove. The old circlips went right in no troubles. So I measured them both and the circlips were 1 thousands too big. I had to go to my ktm dealer ad get the ktm circlips. . They fit fine. I am I convinced if I used the clips that came with the piston they would have jumped out on my at some point. I have never had a problem like this with weisco pistons.