In sweep mode, the note will light up in green while a red LED will appear to the left if it's flat, to the right if it's sharp, or alone if it's in tune. One-button operation toggles through sweep, strobe, and off modes. The unit automatically powers off after 4 minutes to save your battery. The tuner is calibrated to A440 but can be user-calibrated to A435-A445. The peg winder fits virtually all guitar, banjo, and mandolin machine heads. The bridge pin puller gently removes pins without scratching or damage. The built-in string stretcher and long-life hardened steel string cutter help make string changes easy. Planet Waves Pro-Winder Chromatic Pocket Tuner Features: Chromatic tuner with strobe and sweep modes Tuner may be calibrated from A435-A445 Built-in condenser mic Winder, cutter, string stretcher, and bridge pin puller