This is a CMC Triggers Gas Tube known as the AR-15 Gas Tube, model 81622.
Precision machined from 304 Stainless Steel" CMC gas tubes have an extremely durable Nitride finish that increases corrosion resistance" wear resistance" fatigue strength and cosmetic appeal while ensuring consistent gas flow to help your rifle cycle properly. Made in the USA.
Features:
Durable Nitride Finish
Corrosion Resistant
Precision Machined from 304 Stainless Steel