This is a spool holder for 3D printers that use 1515 Aluminium extrusions. They should fit Hatchbox filament (which its spools are 65mm wide). I have not tested it with other spools of filament but I am sure that it will properly hold Hatchbox spools. These should be printed with 25-40% infill density for durability. I designed it to be very beefy and to not bend at all when holding a least 1kg. In order to attach to the extrusions, it uses 2x M3 screws. One from the top and one from the back. I printed mines at 0.2 layer height, 40% infill density. Be sure to enable support material for the lower part or else it will overhang a lot.