The Gen 2 Drop-in captured-spring recoil system helps your AR function more smoothly and quieter without any permanent modifications. The carefully balanced, custom-ground buffer spring, combined with the JP LMOS buffer, greatly reduces friction and vibration – say goodbye to the annoying “spoon over a cheese grater” noise of conventional springs and buffers. Fits buffer tubes for both M4-style collapsible stocks and also, using the included spacer, the longer tubes for fixed rifle stocks. The Auxiliary Spring Rate Kits for the JP Silent Captured Spring allow custom tuning of the device to a given rifle. While the default spring offers 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, particularly for rifles without an adjustable gas block. Benefits of the Gen 2 Captured Silent Springs include: New aluminum guide rod cuts overall weight Heavier masses translate to more buffering mass and chance of bolt bounce Full correspondence between SCS masses and H1, H2 and H3 buffers Interchangeable buffers allow conversion between AR-15 and AR-10 models (and vice versa) Includes spacer to allow for installation in both carbine-length and rifle-length buffer tubes. The standard weight buffer weighs approximately 3.6 ounces. The buffer contains one Tungsten weight, and two steel weights.