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) / Average Service Life: 40,000 Rounds / The longest lasting handgun recoil spring made - our testing has indicated that these springs have a service life up to ten times greater than conventional coil springs. / Improves Cycling and Overall Operation / Improved Recoil Spring Life / .250" Rod Diameter / 17# Flat-Wire Recoil Spring / Compatible with Standard Recoil Spring Plug / Compatible with Shok-Buff® Recoil Buffers / CAUTION: Safety glasses should be worn at all times when replacing or working with firearm springs. Failure to follow this safety precaution could result in bodily injury. / Package Includes: 17# Flat-Wire Recoil Spring.