until recently it stopped working in March 2020. I'm not sure how long they're supposed to run. I have to buy another adapter and it works again for my surface. So I conclude that this is not my Surface Pro or HDMI cable.
Pros
Lightweight and portable adapter to connect Mini DisplayPort (Thunderbolt connector) to HDMI, monitor or projector via HDMI/DVI/VGA cable. Note: Only 1 display output is supported at a time. A separate HDMI/DVI/VGA cable is required. Not included. Not compatible with Thunderbolt 3 (USB-C) ports.