La Crosse Technology TX29U-IT 915 MHz Wireless Temperature Sensor Remote gauge for wireless tracking of indoor or outdoor temperatures 915 MHz transmission for powerful, continuous communication and transmission range is up to 330 feet Works with La Crosse Technology Weather Stations: WS-7013U-IT, WS-7014CH-IT, WS-7017U-IT, WS-7034U-IT and WS-7215TWC-IT Also compatible with WS-7394U-IT-CH, WS-9077TWC-IT, WS-9080U-IT, WS-9117U-IT, WS-9160U-IT, WS-9611U-IT, WS-9640U-IT, WS-9711U-IT; Measures approximately 5 by 1 by 1-1/2 inches; takes 2 AA batteries, not included Tucked inside the paper product manual is where the you can find the screws