Three of them are Toshiba MQ01ABD050 which were originally USB 3.0 externals. Two of them are still connected via USB 3.0 but the third was removed from the case and used as an internal SATA drive. They all run very similar speed wise.
The forth drive is also an external USB 3.0 drive that is connected as an internal, its model is a Seagate ST9640423AS 640GB drive.
I ran 4 Toshiba MQ01ABD050 in RAID 0 just to play with (before being used as storage drives, and to test) and I can't find the screen shot, but I remember pulling some crazy numbers in crystal disk.