The Percussion Plus metallophones are constructed in a similar way to their glockenspiels. They are part of the ever popular Percussion Plus Classic Red Box range, so called because of the instruments' superb tuning accuracy.

Each model features a sturdy wooden frame with the classic Percussion Plus red finish, and contains four separate resonating chambers that amplify the aluminium note bars' mellow sound. Players can also engage a hand operated damper to create special timbral effects.

Combining the PP022 with the PP021 diatonic metallophone creates a fully chromatic scale laid out like a piano keyboard. The 'flats and sharps' expansion is slightly taller than the 'white notes' model allowing the chromatic note bars to overhang.

This model includes 6 notes - C#(Db)29, D#(Eb)31, G#(Ab)36, C#(Db)41, D#(Eb)43, and G#(Ab)48 - and allows room for the F#(Gb) and A#(Bb) note bars that are included with the diatonic half.