If, like your humble editor, you have recently escaped from a state that harbored some form of ban on cosmetic features found on certain rifles, you're about 10 years behind the rest of the country when it comes to adjustable stocks. Everyone else has had the past decade to get re-acquainted with stocks that can be adjusted to fit shooters of different sizes.
Available in either Mil-Spec or commercial (this particular variant is Mil-Spec) sizes, the receiver extension assembly replaces the existing fixed stock on a standard AR. It allows for a wide variety of adjustable stocks to be fitted to one's AR-platform rifle, meaning that custom-fitting the rifle for shooters of varying stature will no longer require tools and extra buttstocks.
The assembly has six positions for adjustment and includes the Mil-Spec receiver extension/buffer tube, receiver lock plate, lock-nut/castle nut, carbine buffer and carbine buffer spring. The buffer tube is Mil-Spec diameter and 6061 aluminum, the buffer spring is 17-7 stainless steel and the carbine buffer weight is 3 ounces. MSRP: $49.99.