hannibalmade by AARK machine, email him at mhughes@aarkmachine.com and he also has a website if you google aark machine. He makes an endcap for your 338 ultra RR suppressor or other RR type suppressors from thunderbeasr arms. You can have an endcap where it’s just that, an endcap, you could also have one where it’s an adapter so you can use the dead air series of endcaps in the center or you can have like the one in the photo. In this one you can thread lock the endcap adapter on and switch end caps in and out as you please but you can also have the RR brake portion. This one is the best and the one I have. Check me out for more reviews here https://www.theoutdoorstrader.com/trade/70462
