Bore: 8.5 mm diameter- Practical aid for musicians to learn or optimise breathing and embouchure for playing a wind instrument at the same time- With 4 balls of different weights and a basket with a sealing cork- First, the lightest ball is placed on the vertical part of the ASTRA and then blown into the horizontal part over its own mouthpiece - as far as the generated airflow is sufficient, the ball is brought into a hovering position over the vertical part - now one can move from the lighter to the heavier balls- The basket can be used to store the balls as well as a catch basket when blowing a ball upwards, if it is put over the vertical part of the ASTRA.- Material: Wood