The Troy .936 low profile gas block is made specifically for bull barrel
rifles that have a greater diameter than the standard AR-15 .750
barrels. 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.
.875 diameter barrels