First Alert ADF-12 BRK/Fire Smoke Alarm Adapter Plugs take the hassle out of replacing 120-volt hardwired Fire smoke alarms that are outdated or expired. Ideal for retrofitting, these convenient smoke alarm adapter plugs eliminate the need for rewiring when replacing an existing Fire detector with a BRK or First Alert alarm. Simply insert the three-pin male connector into your existing Fire ceiling plug, insert the female connector into your First Alert or BRK smoke alarm, and secure the smoke alarm into place. Compatible with a wide range of hardwired First Alert, BRK, and Fire smoke alarms, these adapter plugs can help you save time and installation costs when you're updating the fire safety system of your home or facility. The package includes 12 adapters--enough to install 12 smoke detectors. Package dimensions 1.85 x 8.39 x 5.24 inches, individual unit dimensions are 3 x 1 x 1 inches