M16 / M4 magazine holster. Tested on Magpul Pmags. Has a retention tab. Print upside down so the only thing that needs support is the retention tab. There is an openscad file for the belt clip. Current design fits my 1.75" leather belt. Maybe it will work for airsoft too
update 11/13/2017: One of the angles on the holster was missing. Corrected it. The belt clip scad file, i made the belt loop size a variable called "loop". Change the value to make a belt loop that fits your belt.
Print holster upside down with support in the retention tab area.
Print two belt clips in the given orientation.
I printed in PLA but tougher plastic is suggested (ABS, PTEG).
Put epoxy, gorilla glue or slow cure super glue in the belt clip pocket. Insert belt clips in the pocket. Insert one belt clip higher than the other if you want to give the holster a cant.
Heat retention tab and bend inward if more retention is needed. Hold until it cools.