Been advised to buy one of these for daughter who is going to study overseas which in itself is a sorry state of affairs. The unit is small, sturdy construction and easy to use. I bought this one because of the police spec endorsement and because it was the loudest available. With the original batteries it was not 140db according to the phone app I tested it with - maybe at source it is but I hesitate to suggest trying to keep it at an attackers ear to prove a point. Fresh batteries has resulted in the sound of the alarm becoming louder. Loud enough to severely inconvenience someone. I hope. As for value for money, I've marked it as 5 based on the assumption that it will do it's bit if needed and then it will be worth every penny and some. At this time it has only been tested in the home and it has worked without issue.