This gas block replaces your existing front sight and allows the user to
mount accessories to its four picatinny rails. This gas block can be
mounted either by drilling and pinning it in place or by the use of set
screws (included). Purchase our gas block mounted flip front sight
(YHM-9584) or our solid front sight (YHM-9495) to retain your iron
sights. Made from high quality steel and finished with a Mil. Spec.
phosphate coating. This gas block has a bore diameter of .750 inches.