This is what came with with the Atwood Assembly No. 36720 RV Propane Gas Detector I ordered (and the older Atwood ProTechTor that came with my 2012 25'FB EB).
The bracket that came with the one I recieved isn't a perfect fit in the Airstream cutout for the larger, older ProTechTor; but works. Its close to the floor so you can't really tell that the bracket isn't flush with the paneling at the bottom.
Atwood lists the bracket separately as part number 35181 but nobody carries it and Atwood documentation doesn't mention that it is included with part 36720. I'm wondering if it's inclusion is temporary because lots of listings (Amazon and others) don't show the bracket adapter which you will need to retrofit from the older generation to the newer generation sized detector.
My ProTechTor only made it 3 years before it failed.