The First Alert BRK ADK-12 Smoke Alarm Adapter Plug 12pk easily connects tp competitive Kidde, Fyrnetics and Lifesaver alarms without rewiring. This product is compatible with BRK and Kidde Smoke Alarms and saves time and installation costs when retrofitting existing homes or apartments. Compatible First Alert BRK alarms: SC9120B, 4120-series, 9120-series, 7010-series, 5919, 2002RAC, SC6120B, HD6135FB, RM3. Compatible Kidde, Fyrnetics and Lifesaver alarms: 1235-series, 1275-series, 1285-series, 1276 (PE120E), PE120, PI2000 and HD135F. Maximum of 18 units total may be connected (12 Smoke Alarms, plus 6 other devices. ) First Alert designs and creates safety products that preserve and protect the things that are the most important to you, from your children and family to your home and the priceless memories stored inside.