Triangle caps are mostly for M16A1 triangle handguards. They can often be used with later A2 round handguards. 2 Options:
- Triangle .625 is for pencil barrel profiles that measures .625 at the gas block.
- Triangle .750 is for M4/ M16A2 thicker barrels which are .750 at the gas block.
Round handguards are for early XM's, Carbines, M4, and M16A2. 3 options:
- Round .625 is for XM177 and carbines using a pencil barrel (Does not have 203 notches)
- Round .750 is for using a thicker M4/A2 barrel (Does not have 203 notches)
- Round M4 .750 are for thicker .750 barrels and gas block measuring .750 and is the latest version and has notches to allow for M203 grenade launcher attachment.