The AR-15 lock Ring, also known as a Castle Nut, is made by LBE Unlimited. This component is precision machined from 4140 Steel, A very high strength and durable material. The locking ring is finished with a manganese phosphate coating. This coating gives the part it’s black color and also helps to increase corrosion resistance and resistance to wear.
This castle nut is compatible with any (mil-spec or commercial spec diameter) carbine receiver extension tube. This component is used to secure your receiver extension tube to the receiver, so ensure that your stock does not rotate during usage.
This castle nut has cut outs that allow an appropriate wrench to used to tighten it down onto your lower receiver. A wrench, such as the Magpul Armorer’s wrench, will work extremely well when used on this lock ring.