Low Profile Quad-rail Gas Block for AR15 * Fits 0.75" Regular Barrel and Standard Gas Tube, Replaces A2 Front Sight and Provides 4 Picatinny Rails * Precision Machined from Aircraft Aluminum with Tight Tolerance Control * Hard Anodizing Black Matte Finish, Top Rail Lower than Flat Top by 0.28" * Includes Gas Tube Roll Pin and Locking Screws