The revolutionary and convenient Speed-E is the world's first fully functioning keychain tuner for guitar and bass! Measuring less than 3", the speed-e fits in the palm of your hand and allows guitarists and bass players to instantly tune any "E" on their instrument. The speed-e features: Easy to read backlit LED display Easy access battery compartment (lithium battery included!) High impact ABS plastic construction Quick release keychain There are two ways to tune your guitar using the speed-e: Tune the open "E" strings using the speed-e and tune the other strings by ear.