Producat Name: Magnetic Door Sensor Material: Plastic, Electronic Parts Size: 2 1/2inch x 1 1/16inch x 3/4inch (L*W*H) Color: White Weight: 21g * Suitable to used in apartment, hotel, office, etc; * The Entry Alarm adopts magnetic sensor design to detect any entry from door or window; * Once the two part of this alarm set is separated, it will warning you somebody is in with loudly and harsh sound Package Content: 1 x Magnetic Door Sensor (2 parts ), 4 x Screw Nail Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.