Protec Liberty Trombone Compact Practice Mute (Aluminium)Liberty aluminum mutes are known for their high quality craftsmanship and materials, excellent playability, while being value priced. Compact practice mutes are practically free blowing and allow horn players to quietly warm up before a performance and are small enough to store inside a bell. Key Features: Free blowing and well balanced in all registers High quality spun aluminum Long lasting cork Small enough to store inside a bell Excellent value