Sure looks like its for a relfex can. Sadly I cant say which one, never looked into actual models too much.
The purpose is that it attaches to your muzzle threads but it clocks onto that weird taper to center it at the butt too so that the can is supported at both the base and at the threads to make it a stiffer system while also allowing for more volume without adding even more additional length. Two points of contact is harder to bend than one.