This is a pretty reliable tuner, and great in many ways. The tuner has 1/4" input and output, as well as an output that completely bypasses the tuner (this is cool sometimes, trust me). The unit comes with a power supply that powers the whole operation. In addition, this tuner features an option where you can "daisy chain" up to 7 more BOSS pedals (plus a few others that feature almost identical power supplies, such as the Ibanez tube screamer). This type of tuner is especially useful on stage, as it will cut out the signal while it's on, so the audience doesn't have to hear you tune at all (which is good, because nothing annoys me more when I'm in the audience at a show, and I hear the guitar player have to tune for a minute between every song). There is also a feature that will allow you to use the tuner, but still hear the signal (the aforementioned bypass output). The thing that makes this especially unique is that you can use it chromatically, so guitar players can tune to almost any instrument. You can also hook it up to a microphone, assuming you have the right connections. That way, you can tune horns as well. That's probably the only way you can tune anything but a guitar with this guy. I'd say only guitar players and bassists are really gonna use it anyway, so it's probably fine that there is also a "guitar/bass" setting which will only register the string pitches. Anyway, this is a very useful tuner, especially if you want to use it to power a few other pedals. I'd highly recommend this tuner, it's probably the best one I've used in my 10+ years of playing. It's reliable, hasn't broken on me or anyone else I know who uses it and it gets good results without actually having to let you hear it!