I bought this as part of my emergency kit for a new car. This product represents very good value for money and looks fit for purpose plus, my confidence is boosted by its AA pedigree. There are two main things this hammer is likely to be used for; firstly; there is the obvious hammer which has two pointed heads to give you the best chance of breaking safety glass by concentrating the force of your blow. Secondly; there is a blade at the other end which is designed to help to cut through your seatbelt if you become trapped by it. The device is coloured in day-glow orange to help you find it in an emergency. There is no holder or case supplied so you'll have to find somewhere accessible to store it but where it can't cause any damage to your interior. However, a case or holder could make this device harder to access in a situation when time is at a premium.
I agree with one of the other reviewers on this page who drives a BMW which locks the doors electrically, (my Audi does the same), that in the event of an electrical failure this tool might be the only way out!
I think this is an essential piece of emergency kit which takes up minimal space, and, at the price here, I'd ask can you afford to be without one? Recommended.