Included is a new standard end plate and castle nut so you can stake the whole thing in place. The receiver extension is only 4.5” OAL and 4” when installed, which equates to only ~2.75” horizontal inches beyond the pistol grip. It being easier to store in a ready-to-fire composition is another plus.
You will have to populate the bolt carrier with your own components.
You install the NEA pistol system in much of the same way as a normal receiver extension, with the exception that the buffer retainer pin and spring are eliminated. As such, vertical buffer tube alignment is unimportant. To assemble the weapon once the receiver extension is set up, first install the bolt carrier group (BCG) and charging handle into the upper as normal. The buffer spring is placed over the BCG and then inserted into the buffer tube from the front. Push the upper back until it’s aligned and snap the pins in place. To disassemble (ensure the weapon is cleared, obviously) first both pins must be disengaged and then the upper receiver can be pushed forward and pulled out. You can’t shotgun open the receivers because of the built-in buffer.