Used.  Works like new.   You provide battery and magnets

The Garmin 010-10644-00 Speed/Cadence Bike Sensor in Black is a high-quality accessory designed for cycling enthusiasts. This sensor, compatible with the Garmin GSC10 model, provides accurate measurements for speed, cadence, average speed, and maximum speed. With its sleek design and English language settings, this sensor is perfect for those looking to track their performance and improve their biking experience. The speed comparator feature allows users to easily view their speed in real-time, while the GPS-enabled device ensures precise calculations for a seamless riding experience.