From Sonor – This extra resonator box comes with 7 bars (C#2, D#2, G#2, C#3, D#3, G#3, and also Bb3), and also has space to hold the F# and Bb bars from your diatonic instrument. This allows you to arrange your metallophone in a similar fashion to a piano keyboard – chromatics “on top” and diatonic notes closer to the player. Mallets not included.