Not natural cork.  Bach, Trombone Water key seal.  Contains 2 each 9.5mm x 2.5mm rubber pads.

Fits student & intermediate Bach Trombones:

TBSOL200 Bach Tenor Trombone

TB200B Bach Tenor Trombone

TB200 Bach Trombone

843         Bach Valve Trombone

36CO Bach Convertible Trombone

LTB100 Liberty Tenor Trombone

TB300S Bach Tenor Trombone

TB300 Bach Tenor Trombone