The doors offer ventilation through perforations in the coloured aluminum piece. Behind that piece is a curved piece of metal that is used to put pressure on the installed hard drive. It ensures that the installed hard drive is tight and won't shift or vibrate during operation and transport. There is no provision of a dust filter. As with most other hot swap cages I've used, I expect that dust will build up on the front of the installed hard drives in this cage.
The sides and the top of the cage are made of black aluminum. It looks very sleek, and it's too bad that you don't see the cage as a whole when it's installed in a case. The sides have various screw holes for mounting inside of a case, and the sides are slotted to allow for cases that have rails between drives. I tried test fitting the cage in various Antec, Coolermaster and Lian-Li cases without issue.