One of my very first functional designs. Pop one of the side air grills off your 3D20 and replace it with this. Or hey do both sides! I've always intended to re-design and re-make but it's still holding all the things. So here it stays. Bottom right corner had curling issues. Didn't know of the magical properties of Elmers glue sticks yet. Edit: New version 2 various improvements, slightly bigger pocket with a bottom edge.