Unlike other aftermarket pistons available in today's market, Snyder's Premium Pistons are made by an OEM (original equipment manufacturer). These pistons are the 3 ring type. They come in SETS OF 4 that are boxed and weight matched! Also included are end lock style pins and retainers. Aluminum for snap and power! Standard A bore is 3.875", fits 1928-1934 4 cylinder engines.