RE5F is a 9 position 556/308 AR compatible receiver extension (RE), it is also compatible with Vltor's splendid A5.  REF5 is a collaboration with SOLGW, and is identical to Sons of Liberty Gunworks Loyal 9 A5 RE save for the respective company logo/name engravings. Forward Controls had contributed design input (extra drain holes and softening of sharp corners), there was nothing else we deemed a receiver extension could do better or needed to be improved on, so Loyal 9 / REF5 may look like other REs but with ergonomics and sensible changes, they're made for work, not for show.

RE5F is compatible with 308 ARs and Vltor's A5 system.  For AR15/M16 applications, it must use Vltor A5 or A5 compatible buffers, rifle length recoil springs (Vltor's A5 spring or Sprinco's Green spring).

REF5 is made from impact extruded 7075 aluminum with rolled threads. The interior is dry film lubed, the body diameter is milspec (compatible with all milspec carbine stocks), it has extra drain holes to better and more quickly drain water inside the RE.

An oft-asked question is the difference between Vltor's 6 position RE10/A5SR and the 7 position RE-A5 , as well as RE5F, the answer can be found here: https://www.forwardcontrolsdesign.com/Vltor-RE-A5-vs-RE10-A5SR_ep_78-1.html