Hornady Crimp-On Gas Checks - 100/ct come in a wide variety of diameters, including 0.25, 0.32, 0.38, 0.44, 0.179, 0.243, 0.264, 0.284, 0.348, 0.338, 0.375, 0.416, and 0.475 inches, among others. For hunters and other shooters who do their own reloading, these gas checks are a popular choice due to their high quality and craftsmanship. The checks boost performance of cast bullets. Made from copper, these checks crimp the base of the bullets, thereby providing protection from deformation and hot gases. In addition, the checks help reduce fouling due to the amount of lead buildup in the barrel being decreased.