This piston is intended as a US made replacement for the 12, 20, and .410 gauge factory Saiga piston. It counts a 922 compliance part. High precision machined from pre-hardened stainless steel. It features a concave ring in the face to reduce gas loss around the piston during pressurization which makes it slightly more efficient than the factory part. The increase in efficiency should not be considered as a increase in reliability. If that is what your looking for please take a look at our Saiga Booster Piston by clicking here. The Stainless piston is stamped both with "MD Arms" and a "S" under it and counts as one US made 922 compliance part.