Water key corks for trumpet. Set of 4. I think they can also be used for cornet, trombone, flugelhorn, etc. Outer diameter: 10mm Thickness: 4mm To offer them at a low price, they will be sent by regular mail, so there is no compensation. Please understand. Thank you for your consideration. [Note] We do not accept purchases from those who cannot evaluate immediately after receiving the item. We may respond with an evaluation in some cases. However, this does not apply if you have explained in advance. Thank you.