Sound cards & USB expansion cards are examples of low-bandwidth devices that are commonly used with the single-lane x1 slot. Slot Applications & Sizes. The sixteen-lane x16 slot, on the othsattakihger hand, is mainly used for high-performance graphics cards that need a lot of bandwidth to function properly. These slots differ in physical dimensions; for example, an x16 slot is longer than an x1 slot, which enables larger cards to fit snugly. There are additional PCIe slots made for particular applications in addition to these common configurations. specific PCIe slots.