Direct Kidde Silhouette CO Alarm, Low Profile AC/DC Powered, Operates On A 120V Power Source With A Sealed Rechargeable Battery Backup, Innovative Low Profile Alarm Fits In Most Common Electrical 2-Gang & Plastic, Round Boxes With 3-1/2" Hole Spacing, Pre-Stripped Wiring Harness With Easy Off Cap Does Not Require Stripper Tool.