This is a modular, minimalist, and low-profile filament rack. It can store any number of spools, just print the pieces you need. The rack itself sits only 12mm tall. The spools sit in slots cut into the center of each piece and are held in place by gravity. Despite its small footprint, this rack is quite sturdy.

The rack consists of three parts:

1. An end piece with one flat side and one set of slots
2. A middle piece with tabs on one side and slots on the other
3. An end piece with tabs on one side and one flat side

Each piece connects to its neighbor with a dovetail tab. To store one spool, print only the first and last end piece. To store n spools print the first piece, the last piece, and (n - 1) middle pieces. If you buy more spools, just print more middle pieces!