The Small Brass Witch fits Trombones (small tube)
Brass Witch allows you to remove and attach a pencil quickly. The innovative design won’t scratch or mark up the instrument like the other hard plastic options. 
The use of strong Neodymium “rare earth” magnets is a perfect way to secure the pencil, take notes, and reapply while only using one hand.
Brass Witch users have talked about being ‘converts’ when using the accessory because of the satisfaction of the magnet’s pull. Try it once, and you’ll be under its spell!