Trumpet Mouthpiece Sizes Explained
Updated Nov 11, 2026 · By 
Jonah Mercer · Editorial policy
As an Amazon Associate I earn from qualifying purchases. Buying through the Amazon links on this page costs you nothing extra. Full disclosure
Trumpet mouthpiece sizes are written as a number plus a letter, such as 7C or 3C. The 7C is the size that comes with the Eastar and EASTROCK trumpets, while the PAMPET set comes with both a 3C and a 7C, so you can compare two sizes on one trumpet.
What the number and letter mean
A trumpet mouthpiece size is written as a number plus a letter, such as 7C or 3C. The number marks the size of the cup, and the letter marks the depth of the cup, so two mouthpieces with the same letter and a different number are different sizes. Read both parts together: 7C and 3C are two different sizes, not two names for the same mouthpiece.
Start with the size your trumpet ships with
The Eastar ETR-390 and the EASTROCK trumpet both ship with a 7C mouthpiece, which is the size makers put in the box with a beginner trumpet. Start there and learn the trumpet before you change sizes. A new size changes how the mouthpiece sits on your lips, so give the 7C time before you judge another size.
Compare two sizes on the same trumpet
The PAMPET set comes with a 3C and a 7C mouthpiece, so you can try both sizes on the same trumpet. Swap between them and notice which size you can hold through a longer session. Keep the size that suits the music you play and the way you blow.
Match the mouthpiece to the trumpet
The Eastar, EASTROCK and PAMPET trumpets are Bb trumpets, and the mouthpieces that come with them fit Bb trumpets. Check that a mouthpiece you buy separately fits the shank of your trumpet before you order it. A mouthpiece that does not fit will not sit in the receiver, so confirm the fit with the seller or the maker first.
What you need
Eastar ETR-390 Standard B Flat Trumpet
A Bb trumpet that ships with a 7C mouthpiece, a hard case and a cleaning kit, so you start with the 7C size in the box.
- Case or gig bag included
- Mouthpiece included
- Key: Bb
- Finish: Lacquer
- Valves: Stainless Steel
- 12-month warranty stated
EASTROCK Bb Trumpet Standard Trumpet Set
A Bb trumpet set with a silver plated 7C mouthpiece, a tuning rod and a hard case with backpack straps.
- Case or gig bag included
- Mouthpiece included
- Key: Bb
- Finish: Black Nickel
- 1-year warranty stated
Glory Bb Trumpet
A red Bb trumpet with a case and a pair of gloves, so you have a trumpet to try mouthpiece sizes on.
- Case or gig bag included
- Key: Bb
- Finish: Painted
PAMPET Plastic Bb Trumpet Standard Trumpet Set
A plastic Bb trumpet set that comes with both a 3C and a 7C mouthpiece, so you can compare two sizes on the same trumpet.
- Mouthpiece included
- Key: Bb
- Finish: Lacquered
- 1-year warranty stated
These come from our ranked list Best Trumpet, which compares them spec by spec.
Frequently asked questions
What does 7C mean on a trumpet mouthpiece?
It is a size written as a number plus a letter. The 7C is the size that comes with the Eastar and EASTROCK trumpets, and the PAMPET set comes with a 3C and a 7C.
What is the difference between a 3C and a 7C mouthpiece?
They are two different sizes, written with different numbers and the same letter. The PAMPET set comes with both, so you can try each size on the same trumpet and keep the one that suits you.
Can I use a mouthpiece from another trumpet?
Check that the mouthpiece fits the shank of your trumpet before you buy it. A mouthpiece that does not fit will not sit in the receiver, so confirm the fit with the seller or the maker first.
Ranked trumpets lists
More how-to guides
Product details come from each Amazon listing and can change. Check the listing before you buy.