Constructed from High-Grade Chrome Moly Hardened Carbon Steel. Standard 1/2 x 28 UNEF thread fits the vast majority of AR15s on the market. Additionally, we have added a 3/4-16 outer thread that allows our brake to be mated with our In-line solvent filter, the NAPA 4003 in-line fuel filter as well as may common oil filters available on the market.