Yamaha Custom Series Heavyweight Gold Plated Rim Trumpet MouthpieceThe Custom Series was created with professionals who require superior quality from their mouthpiece in mind. The Custom Series features a new and creative shape and an extra heavyweight and a gold plated rim for players who prefer a focused and centered tonal core. The 16C4 is equivalent in size to a 1. 5C The 14B4 is equivalent in size to a 3C