Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4679673.

This is a mounting rail for the 5.25" cage in an Antec P180 case. These will likely work on other Antec cases of the same era and style, such as the P183.

The 5.25" frame in the pics comes from here: https://www.thingiverse.com/thing:4117845

This will print without supports as long as you print it on its side. I've only tested it with a .6mm nozzle and .35mm layers, but I think it'll work fine with any nozzle and layer height.