This is the standard in trombone practice mutes. Inexpensive but durable. Gets the job done.
"Practice anywhere-in a hotel room, motel room, studio or band room-even in the same house where a baby is sleeping. Disturb no one. Free easy blowing. No resistance in all registers. No one hears you but yourself. Yes, practice anywhere, anytime." -Humes &amp Berg. Made in the USA.