Because USB can do 2 lanes of 10 gbps. So that's 20gbps. 10 < 20. Thunderbolt isn't part of the equation here because it's not a thunderbolt device or thunderbo

Because USB can do 2 lanes of 10 gbps. So that's 20gbps. 10 < 20. Thunderbolt isn't part of the equation here because it's not a thunderbolt device or thunderbolt host (even if the port is thunderbolt capable). The reason it's smaller to go with USB is that AFAIK thunderbolt only bridges to other interfaces like USB or PCIe. So any thunderbolt NIC is actually thunderbolt -> PCIe, then PCIe -> Ethernet. USB is more often interfaced with directly. 2 big power hungry chips vs 1. 1 < 2 so it is smaller. Thunderbolt also carries overhead vs oculink. Thunderbolt tunnels PCIe. The PCIe tunnels the ethernet traffic. Oculink is just PCIe, which is why it's not as hot pluggable but gets significant performance increases for PCIe devices. USB in this case tunnels Ethernet traffic. So thunderbolt NICs have 2 layers, USB has 1. 1 < 2. Less overhead means lower power and less heat so smaller heatsinks, fewer chips means smaller board so smaller device. If more devices had oculink connectors, it's highly conceivable that an oculink adapter would also be smaller than a thunderbolt NIC, because again there's no such thing as a thunderbolt NIC just a thunderbolt -> PCIe -> Ethernet.