Wilson Combat's Custom-Tune Spring Kits are designed to easily and inexpensively improve the action and functionality of your handgun. These quality spring kits feature the finest gun springs available, made from high-tensile spring wire for the finest possible action tuning jobs. Kits include the various springs necessary to assure reliable function, smooth operation, consistency, and long life. Kit Includes:Reduced power mainspring (21 lb) for reduced hammer tensionExtra power firing pin spring (weight not specified) designed for longer spring lifeExtra power recoil spring (20 lb) for increased feeding reliability when shooting factory loadsReduced power recoil spring (12 lb) for light practice loads