We recommend connecting only one external drive at a time. The 6-in-1 USB-C Slim Multiport Adapter has one USB-A 3.2 Gen 2 port (up to 10 Gbps) for high-speed drives and one USB-A 2.0 port (up to 480 Mbps) for low-power accessories. Most bus-powered drives draw more power than the adapter can supply for two drives at once, so a single drive gives the most reliable performance.