These are parts that have been cut out from a one-piece mouthpiece, such as the rim and cup. They cannot be played as is. They can be used as a base for undercuts, etc. The original mouthpieces are, from left to right in the photo: Bach 1C, Yamaha 17B4, and Yamaha 17C4. Only the 17C4 on the far right has a throat size of 25.