This is a small rounded piece of cork designed to fit most trombone and trumpet mutes. They can be attached with pad & cork cement, contact cement, or Shoe Goo. Once dry, the cork can be sanded to match the profile of the adjacent mute corks. Pricing is per piece.
If your trombone or other mute has rather small corks, it's no problem to use the small version of this cork. Although labeled trumpet, the smaller size of these cork pieces can be fine for many larger instruments.