The Tube M4 is a machined MIL-SPEC Aluminum Receiver Extension Tube that accepts all M4-style MIL-SPEC adjustable carbine buttstocks and most commercials. 

Advantages: 

• Six precision-machined notches on the underside provide plenty of options for setting length-of-pull.
• Perfect for a custom build, installing a MIL-SPEC or commercial stock on a civilian carbine, or updating a fixed-stock rifle with an adjustable M4 stock.
• Machined from a lightweight Aluminum extrusion, then hard coat anodized, and dry film lube-coated inside for smooth movement of the buffer and buffer spring.
• Requires carbine recoil spring and buffer, lock ring, and receiver plate, all available separately.  

Suitable for:

Specifications:         

• Material: Machined from a lightweight Aluminum extrusion, then hard coat anodized, and dry film lube-coated inside
• Weight: 103 g
• Hight:  37 mm
• Length:  182 mm
• Diameter: 29 mm