Stonelined Mutes are made in the USA by Humes & Berg Manufacturing Company. Willie Berg invented Stonelined Mutes in 1935, and they have gained a reputation as some of the finest Brass Instrument Mutes available in the World. Sonelined Mutes play perfectly in tune and are easy blowing, and are perfect for the working professional and student alike. Stoneline Mutes offers many different models which produce outstanding varieties of tonal colors for the Brass player. Among the features of Stonelined Mutes is the secret formula used to line each and every mute.