The Clapper valve is a small brass bell screwed to the bottom of the valve. It has the essential feature in any instrument of increasing the harmonic range thanks to the concomitance of the bells incorporated in the valves.
This device greatly facilitates the dynamics of the trumpet itself, giving a greater volume to the harmonics, from note to note. The bells are screwed to the valves.
It is easy to assembly on Stomvi trumpets, just screw it on the lower part of the valve. It is important to check that its assembly is compatible with the instrument, which must have the thread enabled (please consult).