YAMAHA's Silent Brass is a uniquely designed instrument accessory that enables silent practice. - Brand: YAMAHA - Model Name: Silent Brass - Included Items: Control unit, charger, earphones - Design Feature: Circular acoustic opening - Internal Structure: Spring structure Thank you for viewing. I have confirmed that all knobs function correctly and that sound is produced when connected to the actual unit. There is no liquid leakage. However, I am an amateur, so details have not been checked. *I am considering shipping methods, so it will take a little time.