Mouthpiece Mirror Clips on instrument mouthpiece (not delicate pipework) and reflects the position of the mouthpiece relative to the player's mouth. Helps improve mouthpiece centering. Especially useful for new musicians in prevention of bad habits from the start. Easy to use one handed clip on design. Safe (all plastic - no glass), lightweight. Small (mirror is 2" W x 1.5" H) and does not impede view of music and can be quickly rotated 180 degrees out of the way. Fits on Trumpet, Trombone, Euphonium mouthpieces. Not for French Horn. WARNING: has small parts and is a choking hazard. Not for children 3 and under.