I bought one of these a few years ago and love it. It was inexpensive, yet super-easy to use. I use it to tune electric and acoustic guitars, an electric bass, and mandolins. The bass was a little tougher to tune, likely due to the low frequency, but I was able to get a "fix" after repositioning the clip.I've also used this device to "tune" an electric piano... I just placed the tuner on the speaker, struck middle C, and adjusted the tuning potentiometer. Nice.The battery lasted about 18 months for me, and was easily and inexpensively replaced (it uses a popular coin-type lithium battery).I've since bought another one of these for my guitar-playing brother (a nice but inexpensive gift!)