Wolff Reduced power recoil calibration pak for S&W M&P (9mm, .40 S&W, .357 Sig) contains 1 each 12, 14, and 15 Lb. recoil springs. Also included are three standard power striker springs.
For full-size 9mm, .40 S&W and .357 SIG pistols. Factory spring is 16 lbs