BudsGunShop.com - 20mm?

This quad rail has 1913 mil spec Picatinny rails at the 12, 3, 6 and 9 o'clock positions you can mount any size optic mount to the rails as long as it is Picatinny compatible.

Chris, this is a standard Mil-Spec 1913 Picatinny Quad Rail hand guard. It is a drop in replacement quad rail hand guard for carbine length AR-15s, for use with carbines using a front sight base and delta ring. These hand guards are made of an impact resistant fiber reinforced nylon, with aluminum heat shields.