This is a simple filament spool holder for the Makerbot Replicator 1 and clones, based on the amazing Voron 2 printer's design. This holder mounts in the normal Makerbot fashion by inserting into the holes on the back of the printer enclosure. A piece of PTFE tubing is inserted into the holder to provide a smooth durable surface for the spool to rotate on. Use your slicer to mirror the STL to print a second copy if you have a Makerbot Dual like I have.