Icydock's tool and rail free backplane module is called the MB973SP-B. It stores three 3.5" SATA hard drives in the space of two 5.25" drive bays. No hard drive rails or tools are needed, just open one of the three bays and slide a SATA hard drive in right side up, then close the door. On top of that, forced cooling is built in to prevent excessive heat build up, something that isn't always available (or plugged in) within the PC chassis.