This is a 2A Armament Gas Block known as the .875 Internal Bore, model 2A-TIGB-3.
The 2A-Ti gas block is a simple solution for those looking to save weight on the AR-15 style of firearms. By utilizing titanium" weight can be reduced by as much as 40% over standard steel gas blocks. The low profile design works well under hand guards" and anywhere else that space is at a premium. A basic two set screw design ensures a secure fit" and an easy installation. Blue locking compound is recommended.
Features:
Two Stainless Set Screws
Low Profile Design
6AL-4V Titanium
Light Weight