It is called glass setting tape. My car was a post, so I did not have this piece. I did redo the vent windows at the front of the door though. It is the same material.
https://www.bobdrake.com/ItemForm.aspx?Item=B-37193-BWrap the tape around the glass. Firmly install the glass, if the tape is the right size it will take a bit of push to get it in. Be careful, you are working with tempered glass. Then trim the extra material, if any, and you are good to go.
Hope this helps.
D