The circular end cap for AR-15 free float quad rail handguards installs at the front of free float quad rails or KeyMod Handguards without contact to the barrel, for a tighter, cleaner look. 1.75" in outside diameter and 1.1" in inside diameter, it will fit tightly on Monstrum Tactical Free Float Quad Rail Handguards, Free Float Keymod Handguards, and similarly designed free float models. It secures quickly and easily via four set screws with the included hex key, no gunsmithing equipment required. It is made from aircraft grade aluminum and weighs only 0.5 ounces. Available in Black, Flat Dark Earth, and Olive Drab Green. Also Available for LR-308 in Black.