This is a spool holder for the Robo 3D R1( +Plus) which can accommodate larger diameter spools. I had several spools for a Solidoodle Press that never worked. When I got my Robo3D, I wanted to use them. The included spool mount was too small (spool got wedged in the mount and didn't turn well). I found the original for this and just made the diameter larger. Works great.