Yankee Hill Hooded Front Flip Sight Tower with Bottom Rail gives you the best of both worlds. Not only do you gain a flip up sight, but you also gain a bottom rail for flashlight or other attachments. The sight can flip down with the simple use of a button as that button locks it in the up position. Should you want to alter this sight tower, it accepts all standard AR posts and hardware. The great 2 piece design of these sight blocks allows this to be installed over pinned or welded parts. The installation is easy with 4 screws, and the gas blocks fit with a bore diameter of .750 inches. The steel constuction gives you that added strength and durability for nasty field conditions.