DPM Arex Zero 1 Version Standard 4.25in & Tactical 4.9in Mechanical Recoil Reduction System Stainless. The third spring which is contained within the rod controls the movement of the slide so it never rams on the frame. Also included with the system are 3 different in length and strength springs so the user can fine-tune the weapon for his/hers personal standards. The longer spring (more coils) is stronger and has a heavier pound rating than the shorter spring. Specifications for DPM Arex Zero 1 Version Standard 4.25in & Tactical 4.9in Mechanical Recoil Reduction System: Manufacturer: DPM Color: Stainless Fabric/Material: Stainess Steel Gun Make: Arex Gun Model: Arex Rex Zero 1 S Standard Features of DPM Arex Zero 1 Version Standard 4.25in & Tactical 4.9in Mechanical Recoil 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 Arex Zero 1 Version Standard 4.25in & Tactical 4.9in Mechanical Recoil Reduction System What firearm models does the manufacturer say DPM Arex Zero 1 Version Standard 4.25in & Tactical 4.9in Mechanical Recoil Reduction System is compatible with? The manufacturer suggests that DPM Arex Zero 1 Version Standard 4.25in & Tactical 4.9in Mechanical Recoil Reduction System is compatible with Arex Rex Zero 1 S StandardDPM MS-AREX/1: Arex Zero 1 Version Standard 4.25in & Tactical 4.9in Mechanical Recoil Reduction System Stainless