The Wittner GT2 is a simple tuner for guitar and bass guitar. I've only used the GT2 with guitar, but it should be the same either way, although it's not a chromatic tuner so you can't really use it with anything other than a guitar or bass guitar since it just gives you the six notes on a guitar to tune to. It has a built in microphone and runs on a battery, although I don't know exactly what kind of battery. I'm not an owner of the GT2 and have only used it sparingly here and there at the studio where I work. The GT2 isn't the most up to date tuner, but will still do an okay job for simple guitar tuning. It works with a needle that shows you how far off the pitch you are, rather than an LED screen which could be a bit more flexible. It's definitely a tuner that's on the older side, so while I can't say I'm surprised by this, it does indeed limit what it's able to do when compared to more modern tuners. The main reason it's limited is because it gives you the six different guitar strings to choose from rather than giving you every note as an option. If you're using it just for guitar or bass guitar, it should work just fine, although my experience with it has been limited to use with acoustic guitar. I don't know how easy it would be to find a Wittner GT2, but in my opinion it's not worth seeking out. If you do come across one for a really cheap price it might be worth it to scoop it up, but otherwise there are plenty of newer tuners out there that are a lot more flexible and don't cost much at all...