USB31000SPTB is a USB 3.0 to Gigabit Ethernet Adapter that is not currently sold by Digi-Key. Based on the specifications available, Digi-Key part number TL824-ND has been suggested as a replacement.
Both parts are listed with the following specifications.
Compliant with USB 3.0 specifications
Compliant with IEEE 802.3 (10Base-T) and 802.3u (100Base-TX) standards
Supports IEEE 802.3az ( Energy Efficient Ethernet )
For further information see manufacturer data sheet on the product page