Hello. Have had this for years. Just tested and works great. No leaks or issues. 40mm rifle mounted grenade. You attach the muzzle brake to your rifle (14mm negative threads) and keep the "grenade" on your kit. When you need some extra fire power down a hallway or something. Throw the grenade on the muzzle and shoot a bb and it'll cause the grenade to shoot. You can use without muzzle brake and just use your finger or anything to trigger it and or give to a friend and have them shoot it, etc. So gives you the firepower of 40mm grenades without having to attach a heavy 40mm tube to your rifle. These retail for 80 new. PRICE:60 SHIPPED ILL COVER PAYPAL FEES