Kelly Tuba Mouthpieces are made entirely of lexan material. Our Kelly-25 cup sizes are patterned after the Bach series, while our Kellyberg is patterned after the Helleberg series. All cup sizes are sampled by our professional staff and adjusted to produce our final, comfortable, easy-blowing mouthpieces. Kelly's lexan mouthpieces all have standard American-shanks. Our mouthpieces are identical to exacting standards.