When purchasing Wolf or any other brand from eGoods365.com store, you can be sure that (a) you are purchasing from US based company with the most responsive and friendly customer service; (b) an authentic, not a counterfeit and not a refurbished product.
For optimum reliability with hardball and hot handloads. Improves overall function by matching the spring to the specific loads being fired. A wide range of recoil springs; to match your loads and shooting conditions. Fits 9mm and .40 S&W pistols. Recoil Pak - (1) 17 lb., (1) 18.5 lb., (1) 20 lb. and (1) 22 lb. conventional recoil springs, plus (3) extra power firing pin springs. Variable Pak - (1) 10 lb., (1) 11 lb., (1) 12 lb., (1) 13 lb., (1) 14 lb., (1) 15 lb. and (1) 16 lb. variable power recoil springs, plus (3) extra power firing pin springs. Factory springs: 9mm is 17 lb; .40 S&W is 20 lb.