The KynSHOT RB5000L Hydraulic Recoil Buffer is optimized for use with light loads, including subsonic ammunition and .300 BLK. The RB5000L has seen heavy use with civilian competition shooters, law enforcement personnel, and the United Sates Armed Forces. This buffer has patented damping technology to absorb the shock of impact from the bolt carrier's rearward motion and to prevent bolt bounce as a new cartridge is chambered. This model is made lighter and requires less force to cycle than the standard AR-15 KynSHOT Buffer. This is intended for soft cycling or under gassed guns that will not lock back on the last round with the standard carbine hydraulic buffer or heavier buffers. .300 BLK guns running exclusively supersonic ammo may be fine with a standard hydraulic buffer if the bolt cycles firmly and has proper ejection placement.Features Drop-in replacement Reduce felt recoil Improve reliability