Be aware if you plan to use this for upgrading an iMac internal hard drive: The screw holes along the sides of this caddy are not the same size of screw hole that's on the side of a standard mechanical 3.5" hard drive. So, you can't move the iMac mounting studs from the factory drive over to this. Well, not very easily anyway.
Because I didn't want to wait for another caddy to arrive, I used an in-between screw size to widen the threads slightly, then used high torque to drive the iMac studs into the sides. This worked okay, but I wouldn't suggest planning on doing it that way.