This is a 4U, 5x5.25in drive bay mount for 10" racks. This model was created to allow for two IcyDock FatCages, one MB153SP-B and one MB155SP-B, to be mounted to a 10" rack, giving you 8 hot swap 3.5"/2.5" HDD/SSD bays. The 5.25" drive bays are oriented vertically to maximize the 4U space. This mount might work with other 5.25" bay devices, but I don't have any other devices on hand to test.
The author remixed this model.