14 Micro SD, Slots 9 Full Size SD Card Slots Designed for Multiboard V1 has 2 USB drive holders, but they are oversized and not a tight fit, it also has a loose peg slide. V2 is just the two different SD Card slots with a tight fitting Peg holder if you don't plan to use the slide off feature. V3 is the same as V2 except the peg board slide is looser so you can slide it off the peg slide to keep the cards from falling out when removing from Multiboard.