This is a tool based on the Circle of Fifths to aid in transposing chords when using a capo. You simply slide the capo to the desired fret. The dial then shows which chord formation you should play when you have a capo on that fret.
The inner wheel represents the chord being played with the instrument without a capo. The outer wheel shows what chord formation the instrument with the capo would play.
It's a simple, but very useful tool.
Tags: guitar wheel , capo wheel , chord wheel , music chords wheel , capo circle , circle of 5ths , guitar chord wheel , guitar capo circle , capo guitar chords