These are replacement feet for the COMMANDER 5-shelf plastic shelving unit. Their shelves are designed to be modular, but there's no way to purchase additional feet!
There are two foot models provided: short and tall. The short version matches the minimum height that the manufacturer-provided feet will adjust to (7cm). The tall version matches the maximum height I was able to safely adjust the manufacturer-provided feet to (8.5cm).
I printed mine using nylon with 20% gyroid infill. I'm hoping that this will be sufficiently strong for the weight the shelves will be supporting. Please be careful when using these feet with your shelves; this model is provided as-is and I can't make any guarantees about how well they will hold up.
The models were designed in Tinkercad and are available here: https://www.tinkercad.com/things/kGDGr8ql2z5-commander-shelf-feet