3C: The most popular overall size for all trumpet players, student through professional. Balanced playing characteristics make this a good option for any style or genre. Good choice for the advanced student.

5C:  The 5C is often recommended as transitional mouthpiece coming out of a 7C. The slightly larger inside diameter offers a lively and rich tone. Good crossover mouthpiece option that is efficient.

7C: The spring board choice for a beginning student. The 7C size offers a small rim diameter that is manageable for a beginner to control. The depth of the cup provides a full sound is easier for a beginner to manage. This size is generally used by a beginner through professional player depending on genre and context.