Yeah, it is hard to see, but the end of the barrel is threaded and has a thread protector. The muzzle brake is technically a breaching device designed to allow gases to escape when the muzzle is in direct contact with an object. Some people say it does indeed have some effect as a muzzle brake, but the few time that I shot a 14" fabarm wiht one installed, I was hard pressed to tell the difference between it and my brake-less 14" Fabarm. But that might just be me... or maybe the ammo we were shooting on those particular days, YMMV.
Going from memory, I'd guesstimate the brake itself to be about 3 and a quarter to 3 and a half inches long, or thereabouts.