20 GBit/s is great, but so far there's only GigaByte GC-USB 3.2 GEN2X2 add-on card based on AsMedia ASM3242, and a few very high-end motherboards like GigaByte TRX40 Aorus Xtreme, ASUS ROG Zenith II Extreme, MSI TRX40 Creator, ASUS Prime X299 Edition 30, MSI X299 PRO, MSI X299 Creator etc., which all use the same ASM3242 controller. If you do have USB Gen 2x2 ports, this box uses ASMedia ASM2364 controller as a PCIe to USB bridge, and judging by ASUS U32 20G review, it does live up to the expectations. But then again a USB3 Gen2 10 GBit/s box will be cheaper, and ThinderBolt 3 boxes offer 40 GBit/s or 4 Gbyte/s, although for a much higher price.