It's a set of "Tumbler" pen cap that can produce different sound levels. The tip of the cap will jut out, so you can use your thumb to push it with less energy and you can also easily unload or put on it. we use a special color material with different thickness.When the pencil lightly crosses,some different tones of crisp sweet music will come out.12 pens will have 12 different caps with different colors.The "music" pen cap can not only exercise the player's patience,stimulating their auditory development, developing their perception of music, and maintaining their interest in painting.