I bought these for use in an old ATV rebuild where the original piston was still in good shape. Just wanted a fresh set of rings.
After rebuild the engine was continually blowing oil out the exhaust, so I tore it down for closer inspection and discovered the rings are thinner than the stock rings, in particular, the oil control ring is 1.64mm thinner. I reused the old original rings to put it back together and the old girl is running fine again.
The box the rings come in, clearly states "FOR USE WITH NAMURA PISTONS ONLY", which apparently means exactly what it says!
So don't buy these of you are only looking for a fresh set of rings for an old piston.
The included pictures are of the thin Namura oil control ring and of the thicker stock oil control ring.