These gas blocks along with our gas tubes create an efficent and reliable gas system for your AR15 or AR 308 rifle build. – Features: – Fits barrels with .750 Outer Diameter – Constructed from 4140 hardened steel – Aero A Logo – Nitride coating – Low profile for easy fitment – Set Screws are Steel 10-32 x 3/16 Knurled Cup Point – Made in the USA – *Roll pin not included*