What is a mobile rack? I asked myself that same question when Kingwin offered me to review these then I did some research. Well mobile racks is the thing I have been looking for with my complex setup at home. Back couple of years ago I remember looking at those mail catalogs with computer parts much more expensive than what you could find it for online. Well they were referred to as removable hard drive bays back then. I remember looking at those and thinking to myself, damn I wish they were more affordable. Well come four years later I see these mobile racks. The same thing as what I have been looking for back then but way cheaper. $26 get's me one of these things into my computer. Way more than affordable.