You are bidding on a .875 feedneck Stock Class Adapter. This is designed to work with a 10 round tube. (not included) This has an adjustable feed port plug, you can use to turn off the paint from loading into the marker, or turn to easily empty the tube without removing the tube. It also is designed with a thumb screw to be able to loosen for easy removal of the tube and removal from the marker. It can be used in rock forward/backward, or turned to have powerfeed. 3D printed with PLA plastic. (Paintball marker not included, used for demonstration purpose only)