Transmation model 20 pressure gauge. I do not know anything about how these work or how there used. It turns off and on and adjust with adjustment screw. It only would go down to 1.2. Use the photos as the description, they contain more information than I can give you. The battery connection(I believe the negative) is coming apart, care will need to be taken when replacing the battery or the connector will need replaced. I am selling this "AS IS". I will be happy to answer questions on details you may need that I have left out. Thanks for looking!