Yamaha Custom Mouthpiece 16C4-GP Inner Diameter: 17.0mm Throat Diameter: 3.65mm Cup Depth: Medium Rim: Slightly Flat TR-16C4-GP Custom: Easy to play across all registers due to the large inner diameter and medium cup. Suitable for professional symphony orchestra players, producing a large volume. Comparable to a Bach 1 1/2 in inner diameter. Gold rim. Recommended for those looking for a larger mouthpiece, or for orchestral performances. This mouthpiece has been hardly used. It does not come with a case, so it will be wrapped in cushioning material and sent in a small box.