Advantage? 1.The smoke alarm with red LED can remind you which is detecting smoke 2.The smoke alarm has test button allows you to test the unit's functionality monthly. 3.It features a low battery alert to remind you when to change the battery. 4.Easy to install with mounting bracket. 5.It can be used for 10 years. Attention:  1.This smoke detetor is designed to detect smoke. It is Not designed for GAS detection.  2.The smoke detector needs to be tested monthly! If you have any questions about the alarm, please contact us at the first time and our friendly customer service team will respond to you as soon as possible. Specification 1.DC 9V battery operated (replaceable) 2.Photoelectric chamber for early detection from all directions 3.Loud>85dB(A)alarm signal @3M 4.Flash alarm indicator(red LED) 5.Low battery signal alarm 6.Test button for easy recommended weekly testing 7.Safety clip feature,not allow mounting of smoke alarm without battery installed 8.Ceiling mounting 9.Easy to install with mounting bracket 10.10 years product life time 11.Package included: 1*GS536GB Smoke Alarm, 1*9V Battery, 1*User Manual, 2*Screw sets More Detail See User Manual