This BCG for the AR15/300Blk has a phosphate coating and chrome lining that provides the BCG with excellent protection against wear and corrosion, making it a popular choice for those seeking reliability and longevity in their firearms. The phosphate coating provides an initial layer of protection, while the chrome lining offers additional durability and resistance to the stresses of repeated firing. 

9310 Steel Construction, Chrome Lined, Phosphate Finish, Black