Apple describes this adapter as a “Apple USB Ethernet Adapter with built-in 4.6-inch USB cable” and its model number is A1277.
According to Apple, this adapter allows you to “Easily connect your Mac computer to an Ethernet network with the Apple USB Ethernet Adapter. Small and light, it connects to the USB 2.0 port of your Mac and provides an RJ-45 connector that supports 10/100BASE-T performance.”
Source: Apple
