JP Enterprises SCS System Alternative Spring Pack 3 x Springs Silver. While the default spring installed in the JPSCS is selected to offer the best performance for the widest range of configurations a simple disassembly and reassembly of the JPSCS with a slightly different spring rate can yield truly optimized performance. In selecting a spring for your rifle install a heavier spring if you feel the buffer head fully compress and bottom out while firing the weapon. If the bolt will not lock back reliably on the last round fired select a lighter spring. Specifications for JP Enterprises SCS System Alternative Spring Pack - 3 pcs: Manufacturer: JP Enterprises Color: Silver Caliber: 9mm Luger Quantity: 3 Features of JP Enterprises SCS System Alternative Spring Pack - 3 pcs Spare guide rod retainer screw is included in case of thread stripping during disassembly. Package Contents: JP Enterprises SCS System Alternative Spring Pack - 3 pcs 1 x JPSCS-SPRING15-100: Uncolored 1 x JPSCS-SPRING10-100: 1 side red and 1 side uncolored 1 x JPSCS-SPRING10-110: 1 side yellow and 1 side red 1 x Spare Guide Rod Retainer Screw JP Enterprises JPSCS-PACK9: SCS System Alternative Spring Pack 3 x Springs Silver