We purchased a few of these to put on the doors of our day program to insure no one takes off unnoticed as we have a very large number of clients. Today I installed one of these as a test run to see how good or bad it is. It has a very intense sound to it but it sure will be heard in the event that someone passes through the door or window that is not supposed to. If I were a burgular and went through a door or window and heard this, I would fly outta there faster than Superman! You can turn these on and off with a key and it also has a delay setting as well which we are not going to likely use at our day program. It appears to be very well made in my opinion especially for ten dollars. It comes with a reasonable amount of mounting materials including a drilling template and some just in case extra's as well. Takes only two AAA batteries to run it. I am going to get some of these and install some at a friends house as well. This is a very low cost way of putting fear in those who do not belong in your space.