The MalletKAT Octave Expander adds one octave to your MalletKAT Pro, MalletKAT Grand or MalletKAT Express. The three octave MalletKAT is expandable up to FIVE octaves. The two octave MalletKAT Express is expandable up to FOUR octaves. The four octave MalletKAT Grand is expandable up to FIVE octaves. Comes with expander cable and strapping bars. Please Note: all expanders are built with a 3/8 pad height. If your unit has any other pad heights, the expander will not match. Unit dimensions: 15" x 11" x 2.5" Weight: 4 lbs.