The Seiko Digital Auto Tuner for guitar or bass features selectable auto-tuning, manual-tuning, and sound modes, plus a wide, modern tuning range and a wide range of reference tones from low B to one octave above high E. Adjustable calibration from 435-446Hz in 1Hz increments. Also features a built-in microphone and 1/4" input and output jacks. Auto power-off after 20 minutes with memory backup. Includes 2 AAA batteries.