The Ergo 4821 .750 Low Profile Gas Block is designed to fit under the Ergo Modular and SuperLite Rail System as well as most other manufacturer’s free float handguards. Melonite QPQ finish for durability and machined from 4140 chromoly steel with chamfered edges featuring a slip on fit for ease of installation and secured with two set screws. – CNC machined 4140 chromoly steel – Nitride/Melonite QPQ finish – Chamfered edge slip on fit – USA made steel & machined in the USA – Weighs 2oz – Fits under most free float handguards – Internal Diameter 0.750 – Includes (2) set screws for a secure attachment – Accepts standard gas tube roll-pins (roll?pin NOT included)