This is the lower thermostat housing for either the 2wd Vanagon or the Syncro 2.1l waterboxer from 86-92. It is made of aluminum and comes with a new temp II sensor and gauge sensor. It is an aftermarket but the quality level is excellent. If you have a Syncro this is the exact one you should have now.
If you have a 2wd with the original plastic housing you will need to adapt to the gauge sender as it has one pin instead of two. You just cut the sensor plug off and splice a single female spade connector onto the yellow wire with a red stripe and you are good to go. The brown wire is a ground so you just ignore that. The sensor grounds through this aluminum housing instead of a separate wire.