Plastic A GREAT GIFT for homeowners, people who live alone, the hearing impaired, shopkeepers, office workers, anywhere you need a safe guard Easy Installation - The door chime and door sensor are already paired. The first step is to stick the sensor on the door/window (the distance between the two parts should not exceed 0.4 inches), and the second step is to plug the chime receiver into the socket. Installation is completed! Upgraded Battery - Using household alkaline batteries, designed with ultra-low power design, our door sensor chime allows the battery to last up to 7200 times 600ft Wireless Range and Expandable Pairing - All the Satisure brand's door entry chime and sensor alarm can be paired with each other, and one receiver/sensor can pair up to 58 sensors/receivers. With a wireless range of 600ft, it meets the needs of long-distance and multiple pairings for home, businesses, and stores 58 Optional Ringtones and 5 Volume Levels - 58 rich and varied ringtones on door alarm receiver, there is always one that meets your expectations! 5 volume levels from 0-110DB, you can choose silence or loud sound, to meet your needs in daily life! The LED indicator is suitable for the elderly and those with hearing impairments After-Sales Service - Our customers can get 30 days of no reason to re turn service and lifetime enthusiastic after-sales service support from the date of purchase. Our brand has been producing and selling security products since 1993, with absolute experience and skills. Please choose us! If you need the manual or operation video of the product and don't know where to see it, please contact customer service through the order number and we will send it to you at the first time!