Wilson Combat’s flat-wire recoil spring kit .45 ACP 17 Lb. Recommended use- full-Size 5″ .45 ACP shooting 230 gr. hardball equivalent or standard pressure JHP self-defense ammunition with a power factor of 175 000 to 195 000 (Velocity x Bullet Weight = Power Factor). The average service life is 40 000 rounds. Improves cycling overall operation and recoil spring life. Compatible with standard recoil spring plug and Shok-Buff recoil buffers. Includes .250″ rod diameter recoil spring guide and 17# flat-wire recoil spring.