Area 419 hellfire brake, 5/8 24 threads. Up to .30 cal. works great on my 6.5, 270 and 7mm mag. Black nitride finish. I purchased it 2 weeks ago and im not sure why. I have a suppressor coming in the next few months or so. It has less than 100 rounds through it, not a thing wrong with it and it's very effective. Can text or email pics. Have box, paperwork and even the sticker that comes with it. They are 175 new, ill take 160 tyd.