0.8 mm steel with modern case design, very stable enhanced slot plating with EMV-protection double-crimped, deburred edges can be opened on both sides two USB-ports and audio port in the front rubber HDD-cushioning for minimising vibrations no tools required for opening the case air guide for optimal cooling of modern AMD or Intel systems optional: 12cm fan (front/back) for efficient and silent heat reduction detachable and washable front dust filter lockable case 4x 5.25" ext, 2x 3.25" ext., 5x 3.5" int. with rubber cushioning big door with elegant surface texture