Product Detail From Walmart.com With Free Shipping With Sales & Deals $103.95 FREE shipping go to store Walmart.com Trinity Force Gas Block M4/AR15 Quad Rail for .75in Barrel, Black, Low Profile M Trinity Force Gas Block M4/AR15 Quad Rail for .75in Barrel, Black, Low Profile M is a part of the high quality and dependable T8-Tactical Rails from Trinity Force.