How did they make it this small??

TL;DR

A new Realtek-based USB 10 Gbps Ethernet adapter fits in a tiny dongle at $80, replacing bulky Thunderbolt alternatives — but achieving full 10 Gbps requires a rare USB 3.2 Gen 2x2 port.

Key Points

• 1.The WisdPi USB 10 Gbps adapter is small, cool, and cheaper than Thunderbolt rivals. At $80 it undercuts Thunderbolt 10G dongles, runs at only ~42°C versus 'little oven' Aquantia adapters, and draws just 0.86W — its tiny size is possible because it doesn't need a massive heatsink enclosure.
• 2.Actual speeds depend heavily on which USB port you use. USB 3.2 Gen 2 (10 Gbps) ports cap throughput at ~7.4 Gbps; USB 3.2 Gen 2x2 (20 Gbps) ports unlock the full ~9.5 Gbps; Apple's USB 4 controller tunnels USB over Thunderbolt and limits non-USB4 devices to one 10 Gbps lane, yielding only 6–7 Gbps.
• 3.The adapter works on both Windows and macOS without major issues, but driver and display quirks exist. Windows ships an outdated Realtek driver requiring a manual download; macOS auto-connects but shows a '2500-baseT' display bug in network settings, while System Information correctly reports the negotiated link speed.
• 4.The 10 Gbps adapter is only worth it over 2.5/5G alternatives if your network and port support it. A 5 Gbps USB adapter costs $30 vs $80 here and delivers ~4.6 Gbps on Apple USB 4 hardware — only a 1.4x gain; cheaper AliExpress versions using the same Realtek chip exist, and PCIe desktop cards are also available.