Mounts to the top 20x20 rail of your printer. Designed around a 3D Solutech spool, wide enough to hold 2 spools. Has a center divider to keep them from locking together. and support the weight. Uses a standard M4 with T nut at the top to hold it locked onto the rail. Rod can go in from either side and sit flush. If mounting for only one spool? Slide the mounts closer together and skip the middle mount.
Designed to stick out the back (or front) parallel to the bed.
After getting my Tevo Tarantula built, I liked having my dual extruder motors on the top rail. Trouble is, feeding the filament. There are quite a few ways to do this, but for me, I liked this method.