ISMI premium recoil assembly springs for the Glock 43 and 48 are manufactured exclusively with certified aerospace specification alloys; stainless or chrome silicon. Then the springs are heat treated, shot peened and stress relieved after winding to enhance performance and durability. ISMI springs utilize the same design and manufacturing technology as used in IndyCar and Formula One racing. In a typical 500 mile race, a valve spring in an IndyCar will go through more than 2,500,000 compression cycles. Consideration of factors such as modulus, wire diameter, mean diameter, active coils, total deflection, spring relaxation, maximum service temperature, and operating environment; results in you having modern spring technology available for your pistol.Note: Factory strength is 17 lb. DISCLAIMER: This product is not manufactured, authorized, endorsed, or warranted by GLOCK. GLOCK does not warrant or represent that this product is compatible with GLOCK pistols.