Custom BT#4 Trombone Mouthpiece
Inner diameter: 1.027" or 26.0856mm
Bore Size: Standard - .277" or 7.036mm, Symphonic - .281" or 7.137mm
Cup Depth: 1.485" or 37.719mm
The BT#4 is available in both the heavy or light weight blank style. It is also available in either the large shank style or the small shank (tenor).