Both NexTune models include a built-in tone generator for tuning or ear training, and an instrument input as well as a built-in microphone for acoustic tuning. Two simultaneous tuning displays are available: the extra-big LCD with its simulated needle display, or a three-color LED display. Both tuning indicators clearly show how sharp or flat you are, and both give you instant indication when you are in-tune.The NexTune 6z has both Guitar and Bass modes, and the bass mode allows for tuning 5-string basses. The NexTune 12z is fully chromatic and is perfect for most string and wind instruments. Great for beginners or professionals, both NexTunes include Manual calibration from 438 to 443 Hz, and both come with Sabine’s two-year warranty and free batteries.