FreeStyle Libre 3 Sensor 2-Pack The FreeStyle Libre 3 sensor is small, and discreet, in addition to being water resistant. The continuous glucose monitoring sensor is placed on the back of the upper arm for the best results. The thin sleek design of the Libre 3 sensor is so narrow that it is thinner than two stacked pennies. It can easily be scanned underneath clothing. After the 1 hour start-up period, you can wear the sensor for 14 days. Abbott's Libre 3 sensor measures glucose every minute automatically and the most favored feature is that it doesn't require any finger stick calibrations. FreeStyle Libre 3 Sensor Includes: 2 - FreeStyle Libre 3 Sensor