Norco 4U Rack Mount 3 x 5.25-Inch Drive Bay, 10 x 3.5-Inch Drive Bays Server Chassis RPC-450B 4U rack mount design, meets EIARS-310C standard. 3 x 5.25" drive bays, 10 x 3.5" drive bays Easy drive mounting with 24 screwless rails Support EEB (12"x13"), CEB(12"x10.5"), ATX (12"x9.6"), Micro ATX (9.6" x 9.6") motherboard 2x120mm front fans, 2x80mm optional rear fans for better ventilation Front accessible USB port 2x120mm front fans, 2x80mm optional rear fans for better ventilation