Warburton sax neck set, fits Selmer alto saxophones, content: copper neck, tenon for Selmer instruments, 3 initiators (mouthpiece receivers) F47, CA48, S48 with different backbores, CA48 (1/3 cylindrical): warm and uniform timbre across the full range, perfect for classical music, F47 (2/3 cylindrical): the lower register is big and warm with an excellent subtone and the upper register is fluid and singing, perfect for jazz, S48 (straight cylinder): most balanced in terms of lows, mids, and highs in the sound, perfect for contemporary styles