These LTO cases are for use with half-inch LTO tapes. These LTO cases are compatible with all LTO tapes (LTO-1, LTO-2, LTO-3 and LTO-4). Cases are necessary for tape cartridges because not only will they protect your tape cartridges and the valuable data within from shocks (due to accidental dropping or during shipping, etc) but they also provided a limited amount of protection from environmental conditions (such as heat, humidity, etc).