Peterson strobe tuners respond at the speed of light to display relative tuning of any audio source to 0.1 of a cent (1/1000 of a semitone) accuracy! In addition to the visual strobe indication, the Autostrobe 590 can function as an audio tuner by means of an Audio Out section, which combines input sound with reference-pitch tones into headphones or an internal speaker. As with all the new AutoStrobe models, the Model 590 allows students, technicians, and musicians at all levels to utilize automatic (hands-free) note selection for fast, accurate tuning of instruments. This feature also permits real-time display of intonation and, combined with the Audio Out function, provides a great way to improve performance  Automatic Note Selection Automatic Note Tracking - the audible tuner "tracks" the automatic note select                                                                                                                                                                                                                                                                                                                                           width 9 inches x length 19.80 inches x  height 7.2 inches will ship carefully i will include insurance of full purchase price.