The TopStop is a one-piece, snap-on cover for the upper receiver of a 5.56mm AR upper receiver. It is injection molded from high-strength nylon. It attaches over the bottom and rear of the upper receiver when the rifle is broken down, and keeps the charging handle and bolt group from sliding out of the upper. It also helps keep the dirty lube from dripping out of the upper and all over your hands and rifle case, as well as preventing dirt, sand, and other debris from getting into the receiver.
Interessante per i GBB.