The Troy .875 low profile gas block works on both .223, 5.56 and .308 bull barrels (As well as other calibers). Finally there is an option for users who desire to replace their default gas blocks, or fixed front sight gas blocks to utilize a free float rail system that installs over the gas block.
Features and Specifications:
Manufacturer Number: SGAS-875-00BT-00
.875 diameter barrels