21010167 Features: -Includes end of life and end of hush features. -10 Years of battery life. -Sealed-in lithium power supply. -Advanced photoelectric sensor detects particles associated with slow smoldering fires. -Alarm automatically activates when attached to mounting bracket. -Test and hush button. Product Type: -Smoke Detector. Orientation: -Wall/Ceiling Mounted. Power Source(s): -Lithium-Ion Battery. Mounting: -Universal Mounting Bracket. Compliance, Standards: -UL Listed. Dimensions: Overall Height - Top to Bottom: -1.4". Overall Width - Side to Side: -5.22". Overall Depth - Front to Back: -5.22". Overall Product Weight: -1 lbs.