Simplisafe Extra Entry Sensor<div style="text-align: left;"><strong>[Product Information]</strong><ul><li id="replacementPartsFitmentBullet" class="aok-hidden" data-doesntfitmessage="We're not sure this item fits your " data-fitsmessage="This fits your "><span class="a-list-item"><span id="replacementPartsFitmentBulletInner"><a href="#" class="a-link-normal hsx-rpp-fitment-focus">Enter your model number</a>to make sure this fits.</span></span></li><li><span class="a-list-item"> Easy to install on every type of door or window </span></li><li><span class="a-list-item"> The magnet goes on the door or window， and the sensor goes on the frame (or vice versa). Magnet can be placed up to 2 inches from the sensor， so sensors fit on all types of doors and windows. SimpliSafe sensors come with the battery pre-installed and adhesive tape pre-applied， making installation a snap. </span></li><li><span class="a-list-item"> When your system is OFF and a door or window opens， the Base Station will sound a door-chime so you’ll know if someone is entering. </span></li><li><span class="a-list-item"> The sensor detects whenever the magnet moves more than two inches away from it- so it knows whenever the door or window opens. </span></li></ul></div><img src="http://ecx.images-amazon.com/images/I/41lo0n5G7lL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/319m%2BLbQXhL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/31xJbbBesYL.jpg" noproxy>