Choosing the right gas block for your build can have a positive impact on the performance of your rifle as well as its appearance. The gas system is a crucial component of your AR-15, and the gas block is a crucial component of the gas system. In truth, this tiny AR-15 component can reduce recoil and wear, boost reliability, and do much more besides. Typically, a conventional gas block will only let a certain amount of gas through per cycle. Some of them let in excessive amounts of gas. The blocks on a low-profile rifle are precisely machined to take up as little room as possible along the barrel.