This specific DPM Mechanical Recoil System (Captured Version) it is based on the DPM Patented (U.S 7.380.487 B2 and US 7.493.845 B2) Multi-spring Recoil Reduction System and functions due to the multi spring intricate rod (3 springs). This system offers almost double force at the end of full open position of the slide. Compared to the factory OEM spring provides additional force that stops the violent rams on the frame. From the above effect the slide stops smoothly on the frame and offers less recoil. Further the moving parts of the pistol are protected, offering longer life to the pistol. Finally the design of DPM Captured Version makes it easy to install on the frame. Specifications for DPM Mechanical Recol Gen 4 Captured Version Reduction System: Manufacturer: DPM Color: Stainless Finish: Black Oxide Fabric/Material: Stainess Steel Model Generation: 4 Condition: New Features of DPM Mechanical Recol Gen 4 Captured Version Reduction System Faster follow up shots. Improved firing speed. Slide and frame protection. Elimination of jams. Significant recoil reduction. Better double-tap concentration. Better control and greater accuracy. Package Contents: DPM Mechanical Recol Gen 4 Captured Version Reduction System This product is compatible with the following gun models: Glock 20, Glock 21, Glock 40, Glock 41, Walther Q4, Glock 19, Glock 23, Glock 32, Glock 45, Glock 19X, Glock 31, Glock 37, Glock 17, Glock 22, Glock 34, Glock 35