B â™ / Convertible model. Valve system is 4 pistons. The bell has a yellow brass diameter of 443 mm, the bore size is first to third = 18.5 mm, and the fourth = 19.5 mm. With 2 blowing pipes.
Custom series B â™ / F compensating system. Valve system is 4 pistons. Bell has a yellow brass diameter of 300 mm, a bore size of 15 mm (No. 1 to No. 3) / 16.8 mm (No. 4), silver plating (partial gold plating) finish.