Set of 4 tire valve caps New Comes with its special tightening key I sent one and after it arrived I discovered that it requires removing the tires to install it And I thought it was the external type So I didn't use it and put it up for sale The air pressure sensor fits on it I don't know its size, but I took a picture with an AAA battery for remotes to show its size There are no writings on it, only the word 'Short' written on the box