Vandoren CM4138 M13 13 Series Profile 88 Bb Clarinet Mouthpiece Rich and colorful sound with a very precise response Tip Opening - 100.5 (1/100mm) Long Facing Works best with Vandoren #3.5-#5 Reeds Profile 88 Beak; Series 13 A=440 Vandoren M13 Bb Clarinet Mouthpiece.