These wrist pins fit all of stock Ford 1600 "Kent" crossflow pistons as well as the original (May 2023 and older) forged CP / Ivey pistons which used Spiroloc retainers. They are optimized for use with Spiroloc Wrist Pin Retainers (Part No. 161-19-Sprl, sold separately) and do not work properly with current (June 2023 and later) Ivey pistons which use Wire-loc retainers. Sold individually.