Used Booster Ring for Cornet Mouthpiece One-owner item (myself). By attaching a booster to the shank of a cornet mouthpiece, the weight of the mouthpiece itself increases, removing unwanted noise from the lips and transmitting more regular vibrations to the instrument. Please refer to the photos for the condition when fitted to a mouthpiece. (※The mouthpiece in the photos is not included in the product.) Recently, boosters that are often sold are very light, and heavy ones like this product are apparently not currently sold. If anyone is interested, please let me know. Thank you. m(_ _)m