Does gigabit ethernet to thunderbolt adapter work with old ethernet? Does Apple's Gigabit ethernet to thunderbolt adapter work with old types of ethernet that are not gigabit?

I am wondering because I want to use it with my 2015 macbook pro, wondering if I can connect to a non-Cat6 cable (my router doesn't support gigabit ethernet)
From Thunderbolt to Gigabit Ethernet Adapter


  The Apple Thunderbolt to Gigabit Ethernet Adapter lets you easily connect to a high-performance Gigabit Ethernet network. Small and compact, it connects to the Thunderbolt port on your Mac computer and provides an RJ-45 port that supports 10/100/1000BASE-T networks.


So the answer is, yes it will work. It will provide the bandwidth up to the supported bandwidths 10/100/1000BASE-T as applicable.