CN5F (Castle Nut, A5, Forward Controls) is an extended version of CNF Forward Controls Design (FCD) have been making since 2018. CN5F is designed specifically for the superb Vltor A5 system, CN5F is 0.1" longer, and is as long as FCD can make a castle nut while ensuring backward compatibility, and the stock's ability to fully collapse on Vltor's RE-A5 and FCD's RE5F. Note: not all stocks will fully collapse on A5 compatible REs. For more information on the differences between RE-A5, RE5F and RE10/A5SR, please follow this link: https://www.forwardcontrolsdesign.com/Vltor-RE-A5-vs-RE10-A5SR_ep_78-1.html CN5F aims to cover as much of the threaded area of a receiver exte Mfg: Forward Controls Design