This Guntec USA castle nut is a mil-spec replacement for AR-15 carbine (CAR/M4) buffer tubes. The castle nut locks the receiver end plate and buffer tube in place on the lower receiver, so a solid one keeps the stock from loosening. Made from steel in the USA.
- Brand: Guntec USA
- Type: Castle nut, mil-spec
- Fits: AR-15 CAR/M4 buffer tubes
- Material: Steel
- Made in USA
- Manufacturer part number: CASTLE
