I'm new to Tesla so I'd not heard of the system used to monitor tire pressure (TPSM) before. Being the kind of person who likes to take pictures I got a few shots of a Tesla Model S wheel with a pressure sensor installed for my own use but thought I'd post them here in case anyone else wonders what the unit looks like and how they are mounted.
I bought the wheels from a guy who said he took them off his car right after driving it home a while ago (he replaced them with aftermarket wheels). He did not say what year the car was. He removed the sensors before sending the wheels to me so the sensor shown is a new one I just had installed.
Those are the Continental TPMS sensors (newer sensors, for VINs 50900 and above). The easy way to identify the Tesla Continental sensors is the large "433" on them. The older Baolong TPMS sensors (for VINs prior to 50900) do not have this marking.
I just bought 4 sensors myself in Fremont. Their waiting for my 4 dark gray 21" wheels which I bought for $940 shipped.