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First Alert 9120B Smoke Detector, Hardwired Alarm with Battery Backup, 6-Pack - Smoke Detectors - Amazon.com
SITERLINK Smoke Detector Hardwired, Smoke Alarm Interconnected with Battery Backup, Photoelectric Fire Alarms Smoke Detectors with LED Lights, UL217 Listed Fire Alarm for House, GS517 - Amazon.com
First Alert 9120B Smoke Detector, Hardwired Alarm with Battery Backup, 3-Pack - Amazon.com