Wilson Combat's Full-Size 5" .45 ACP shooting 230 gr. hardball equivalent or standard pressure JHP self-defense ammunition or 10mm shooting target ammunition with a power factor of 175,000 to 195,000 ( Velocity x Bullet Weight = Power Factor ). This is a balanced kit containing two SHOK-BUFF buffers and one heavy duty recoil spring. The SHOK-BUFF should be changed out every 1,000 rounds and the recoil spring every 2,000 rounds.