CAD designed and built to Aerospace specifications from chrome silicon, corrosion resistant, stainless steel or chrome vanadium for maximum durability, consistency and reliable performance. Built to aerospace specifications; heat treated, shot peened and fully stress relieved to minimize spring set. GLOCK® RECOIL SPRINGS - Flat wire, chrome vanadium alloy,, wound to fit factory diameter guide rod of .250" or less. GLOCK® 17 fits large frame 17,17L,20,21,22,24,31,35. Factory weight is 17 lb. GLOCK® 19 fits 19,23,25,32. Factory weight is 18 lb.