Both the P182 and the P190 employ trays for the install of hard drives. Each case has two trays, one each in the lower and upper chambers. These trays slide in and out, and are fixed in place with a single screw. This makes installing and removing hard drives easy.
The drive tray for the lower chamber fits 4 3.5" hard drives.
The drive tray for the upper chamber fits 2 3.5" hard drives. A nice touch is that this drive tray has a plastic storage box on the back where extra screws can be stores.
The screws used for mounting hard drives are longer than normal screws, and thus are propietary. They are used to mount hard drives in conjunction thick rubber grommits. Hard drives are a big source of case vibration and noise, and this helps to reduce those elements.