The micro technology used in this alarm provides features that are similar to ones found in alarms 3 to 4 times its size. It has a PIR motion detector, a 100dB personal alarm and a LED flashlight. It is great for home, business, hotel and dorm rooms. It can be used as a personal alarm for self defense, or set the motion detector to protect your home, apartment, or in a hotel to protect your valuables while you are out of your room. The motion detector can also be used to prevent children from wondering into a dangerous area, such as a pool. The alarm operates on 3 AG13/ LR44 button batteries that are included. The dimensions of the alarm are 2 and five-eight inches x 1 and three-eight inches x seven-eight inches.