4U, EE-ATX (13.68" x 13"), E-ATX (12" x 13"), ATX (12" x 10"), 24 x 3.5" hot-swap drive bay, 24-port 4U SAS3 12Gbps single-expander backplane, support up to 24x 3.5-inch SAS3/SATA3 HDD/SSD, 1U 1280W Redundant Platinum 95%+ Super Quiet Power Supply with PMbus, 7 full-height & full-length expansion slot(s), 3 x 8cm hot-swap redundant PWM cooling fan(s), 10.5K RPM Upgrade for X11: FAN-0185L4, 2 x 80mm rear hot-swap exhaust PWM fan(s)