As far as I know, all the wrist pins are the same diameter, but I've seen a couple of different lengths, depending on what piston you have. Briggs made about 15 gazillion different width of rings, which is why the code is so important. If you buy an AVS piston and the matching wrist pin, the rings should be included in the box with the piston. Just save the box, with the part number, in case you ever want to order another set of rings. Briggs pistons come in standard bore and .020 over. Make sure you have the long ARC rod.