The FreeStyle Libre 3 system is painless to apply1 and wear1 with a simple 1-piece applicator. There is a needle (sharp) in the applicator to insert the filament in the back of your upper arm so the sensor can monitor your glucose.
1 Alva, Shridhara, et al. "Accuracy of the Third Generation of a 14-Day Continuous Glucose Monitoring System." Diabetes Therapy 14, no. 4 (2023): 767-776. https://doi.org/10.1007/s13300-023-01385-6.