Picked up a JMAC X37 adapter and sleeve . Its a rear cap/brake for a ASR thread pattern ( 1 3/8 threads ) tube. JMAC says its only for M92's and they wont work on M85's and I know why they say that. The M92 barrel extends to the end of the flash hider while the M85 does not. . The X37 is supposed to index off the barrel face. Helps in barrel to bore alignment. In any case I'm running a modular 30 cal form 1 silencer and a little misalignment isnt an issue.