FOSBOS is an completely free organizational system, every model is open sourced including both fusion 360 file and the step file. All the drawers are designed after the gridfinity standard.
This model is a bin for storing your spool holder that fits in any of the drawers that is at least 4u high.
There are 4 different bins, 2x3x4u, 2x3x6u, 2x3x8u and 2x3x10u.
Please have a look at the assembly model(here) for more information