La Obrac non fà attualmente i bocchini slap monette. (tranne forse il B2S3 (12S3))
Il B4S è un modello fatto per Lew Soloff (la S sta proprio per Soloff), è una copia di un Bach 3C Mount Vernon.
"B4S Very similar to the B4 but with less bite to the rim and a slightly brighter sound. This mouthpiece is as deep as the B4, but has a more efficient shape to the cup, making it especially good for upper register work. This rim and cup design is used by New York jazz and recording artist Lew Soloff. "