This is a balance weight for Getzen and Edwards trombones. Made of lacquered brass. Includes 2 halves, 2 screws and 2 stickers. This is a useful accessory when paired with the Getzen 3047AF straight neckpipe. It'll help bring proper balance to the straight Bb trombone when helps reduce tension in the player's shoulders and upper back. True story.
It's not easy to remove this balance weight once the stickers are applied. Options include mounting this on the neckpipe brace instead of the tuning slide brace. You can skip the stickers (though your style will be -1) or don't remove the sticker backing and then attach the stickers with a lighter adhesive...a few drops of shoe goo or nail polish or double sided tape might do it.