Our take:  The Golden Eagle M4 / M16 Hop-Up Chamber Set comes with everything you need to install it right out of the box, including the bucking, hop-up chamber, adjustment wheel, and bucking lock clip.  This airsoft internal part is perfect for replacing damaged hop-up units or for building a custom AEG from the ground up!

Features:
- ABS plastic construction
- Hop-up adjustment wheel
- Rubber bucking included
- Compatible with most M4/M16 AEGs

Package includes:  Airsoft hop-up chamber, wheel, adjustment wheel, bucking lock clip

NOTE:  This hop-up chamber assembly does not include the bottom piece that connects into the lower receiver.

Package weight: 1 lb