The Seiko ST01 Tuner is a handy personal tuner complete with keyring that you can take with you wherever you go. Ultra Compact & Easy to Use with a Metal Faceplate. Simply, press power switch to turn on/off. Input sound of instrument into built-in microphone. Indicates name of note and deviation in cent. LED light changes color when in tune. Easy to use, readily accessible, and the key ring is included.