Screwless Front Panel Screwless Side Panels Screwless 5.25' Drive Bays Screwless 3.5' Drive Bays Screwless PCI-E Expansion Slots 3.5' Drive Bays x 3 Internal 2.5' x 1 ?Intel Certified TAC 2.0 Qualified for TAC 2.0,a mass ventilation hole side panel design that strengthens thermal efficiency and cools down the entire system. ?80mm or 90mm Rear Fan (Optional) ?USB 2.0 x 2 ?HD Audio ?Optional USB 3.0 x 2 eSATA Chassis Intrusion Switch 3.5' to 2.5' HDD / SSD Bracket Supports 2.5'x 2 Optional 60 mm Fan x 1 (60 x 60 x 10 mm, 2500rpm, 20dB Fan, 4 Pin Power Connector)