UD AR-15 SOLID ADJUSTABLE GAS BLOCK The UD Gas Block allows you to custom tune a rifles performance to a specific rifle and ammunition combination. Having a gas block adjusted precisely allows the bolt carrier group to cycle only hard enough to extract and feed the new round into the chamber without hammering hard against the receiver extension. The adjustability can easily improve the performance of any rifle, but it is especially important for the competitive shooter or when using hotter ammo or a suppressor which sends significantly more gas rearward. The UD Gas Block allows for a smoother, cleaner and cooler cycle which improves performance by leveling the feel of the shot and re Mfg: Ultradyne Usa