We have two thread patterns for AR10 Armalite and DPMS if your upper is not patterned off of one of these it will not work, you will low profile gas block for this forend.
-DPMS #15060 with a 1 7/16"-16 TPI. Will have 22 holes on perimeter.
-Armalite #15061 with a 1 7/16"-18 TPI. Will have 20 holes on perimeter.