This is a custom-made rotary valve cap for a trombone. I think it will make your trombone look cool. It's compatible with B&S tenor trombones and all trombones with Courtois rotary valves. I only opened it to take pictures and haven't touched it since. I'm also selling another of the exact same item, but don't worry about that; I accidentally bought two. Bass trombone players are welcome to buy both. Feel free to make offers on the price.