Who's that knocking at your door? You will never guess again with Krown Door Knocker 125 alerting system. This door notification system for the hearing impaired features an LED light that flashes. This ultra bright LED visitor indicator on this hearing impaired door notification system can also be used as a flashlight in power outages. This daily living aid is portable and convenient for travel, so be sure to have an extra one on hand to take on the road for use in your office, dorm, hotel, etc. The Krown Door Knocker 125 uses a 9V battery (not included). Includes 2 installation brackets. The alerting system measures approximately 3 x 3 3/4. Total shipping weight .25 ounces. Product dimensions (imperial): 3.75 inch H x 3 inch W Product dimensions (metric): 95.25 mm H x 76.20 mm W.