You will notice that the manufacture date on the box is Aug 2014, so the batteries in this should be good for 10 years or so from that date .....
This is an important point when buying a used ( or new ) alarm from fleabay or a recycler, how old is it ?
This unit requires a nut to attach it to the support.
( I have often been called a nut, so I should be able to attach it to the support with no assistance )