The Boss TU-12EX is a chromatic tuner for electric, acoustic, and bass guitar. The tuner has both 1/4" inputs and outputs, so unlike most tuners of this kind you can actually plug through it. It can be powered up by a nine volt battery or power supply, and has an auto off mode that will power it down to save battery when it is not being used. The TU-12EX has separate modes for guitar and bass guitar, each with the ability to choose your tuning type and if you want to use it as a chromatic tuner or as one specifically for bass or guitar. The tuner also has reference tone for tuning by ear in stead of with the needle. However, the needle is quite accurate and the tracking is great on it. The Boss TU-12Ex is overall quite small and fits in my hand easily. While I enjoy using the tuner since it is user friendly and pain free generally, there are a few things that I don't like about it - mainly the price. For this price you could get the Boss TU-2 pedal tuner and save some money! In my opinion the TU-2 is a much more useful tuner because you can use it with your other pedals and it will also power up other pedals. I guess I can see why you would want something like the TU-12EX rather than a stomp box tuner, but common logic should say that these kinds of tuners should cost less money, not more! Don't get me wrong, the Boss TU-12EX is a great tuner that will get the job done and do it while looking great and offering up a good amount of features, but I just couldn't justify a tuner like this at this price considering what else is out there on the market...