So my optical drive slot was getting stuck, so I took it into the Apple Store to get it fixed. Turns out you need to replace the entire chassis if that thing breaks! Well I got my machine back today. They replaced the entire chassis, with a new… -Chassis -Side cover -Four new HDD sleds (when I had none installed) -3 PCI cover brackets (I guess you'd get 4 if you only have a single slot GPU) -Optical drive sled -Motherboard brackets -Fans All for $150 including tax. So for $150 (less if you don't have tax in your state), if your mac pro is in poor shape, or lost some sleds, etc., you get new ones. I don't think anyone should abuse this, but I thought this would be good to know.