or 
The TU-3 incorporates a convenient Note Name Indicator that can display notes of 7-string guitars and 6-string basses, while the Flat-Tuning mode can support up to six half-steps.
It’s the new-standard tuner that no guitarist or bass player should be without!
Features:
· 21-segment LED meter with brightness control
· High-Brightness mode enhances meter visibility outdoors
· Accurate to +/- one cent
· Accu-Pitch Sign function provides visual verification when tuning is complete
· Chromatic and Guitar/Bass mode (tune by string number, with support for 7-string guitars and 6-string basses)
· Flat tuning is supported with Guitar Flat mode, which allows for “drop” tunings up to six semitones below standard pitch
· Tuner automatically mutes when the tuner is on
· Supplies power for up to seven BOSS compact effect pedals
· BOSS five-year warranty
