ZEV Recoil Springs are custom designed for high performance in our OZ9 platform. When combined with our stainless steel guide rods they will provide superior performance and looks. The 18 lbs spring is found in our OZ9 V2 and OZ9C V1 platforms and is a great upgrade option for Glock 19 pistols. This is the recommended recoil spring for all OZ9 Hyper-Comp pistols. Compatibility Glock 19 (1st - 3rd Gen) Glock 19C (1st - 3rd Gen) OZ9 Compact OZ9 Hyper Comp