Air filter holder (17 x 12 cm) with 3mm slots

A simple 17 x 12 cm box with a hex pattern on both sides to hold some kind of air/dust filter. It also has 3mm slots on the sides so it can be easily mounted. Outer depth is 21mm, inner depth where the filter goes is 15mm.

I use it stuffed with a kind of dust filter fleece and mounted it on the back of my 3D printer LACK enclosure.