3.5' hard drive rack for 3-liter Slim PCs Shuttle accessory PHD4 allows for installation one 3.5' hard drive for 3-liter slim PCs (except XH61V/XG41). No other drives (i.e. DVD drive or 2.5' HDD/SSD) can be used while PHD4 is in use. Full spec: http://au.shuttle.com/products/productsSpec?productId=1863