Model No. / Depth of Cup / Approx. Cup Dia. / Rim Shape / Throat / Backbore / Description 1G / Deep / 28.00 mm * Among the largest and most powerful bass trombone mouthpieces produced today. 1-1/4G / Deep / 27.50 mm / Medium thin, well rounded. * 0.276" / 429 / Cup diameter is smaller than No.1G, but still very large and deep, with the sonority preferred by the modern American school. 1 - 1/4