CN5F (Castle Nut, A5, Forward Controls) is an extended version of CNF they've been making since 2018.  CN5F is designed specifically for the superb Vltor A5 system, CN5F is 0.1" longer, and is as long as they can make a castle nut while ensuring backward compatibility, and the stock's ability to fully collapse on Vltor's RE-A5 and their RE5F.  Note: not all stocks will fully collapse on A5 compatible REs.

CN5F aims to cover as much of the threaded area of a receiver extension (RE) as possible.  It could be made longer, but it will run into backward compatibility issues with some REs' timing when installing the castle nut and end plate on the RE.  CN5F is made specifically for the Vltor A5 system, and it will allow even the longest carbine stocks to fully collapse on RE-A5 and their RE5F.  While CN5F will also work on standard TDP spec length RE, the additional length of the castle nut will prevent the carbine stock to fully collapse.

Other than its length, CN5F shares common features with its smaller brother, CNF.

The TDP spec castle nut is a simple and robust fastener that is almost perfect for the job it's tasked to perform.  Over the years, they've consistently come up with two minor gripes, first is its staking notches seem rather shallow and short, second is they don't enjoy using the castle nut's wrench notches as serrations (their fingers invariably find their way to these sharp cutouts) to rotate it towards to the end plate while installing it.

CN5F (Castle Nut, Forward Controls) is based on the TDP spec castle nut, with couple of changes:

• 0.1" longer.
• Staking notches angle changed from 45 to 30 degrees, this results in longer (25% longer than TDP spec) and deeper notches than found on TDP castle nuts.
• Number of staking notches increased from 3 to 4, spaced equally on the CNF. The castle nut is to be staked in two places, they're not advocating staking in more than two places, CNF's 4 staking notches mean that, at all times, 3 will be visible and available for staking, it simply gives the user more staking location options.
• Coarse serrations on the wrench side of the nut, a single use feature to make it easier while rotating the CNF towards the end plate.

It is their opinion that a castle nut should be staked per TM, CNF's and CN5F's longer and deeper notch reinforces the belief, that once installed and staked, it will not loosen without the user's deliberate action.  They like the idea of quick detach, but some things on an AR are meant to stay put, and considerable effort was made to ensure that by the original designers.  CNF  and CN5F are a continuation and evolution in that direction.

CN5F is billet machined in 4140 PH steel.  As with everything Forward Controls Design produces, it is proudly made in the USA. 

Specifications:

• Weight: 0.51oz
• Material: 4140 PH  

Please NOTE:

• CN5F will not allow most carbine stocks (except B5 Bravo, Bravo can fully close) to fully collapse, CNF will.
• CN5F is incompatible with Magpul's PRS Lite stock.