This is a a vintage Meyer Tru-Flex Brass Alto sax mouthpiece. These mouthpieces are very rare, and this is one of the only ones we have ever seen. It is marked a 4, and measures out at.070" The mouthpiece plays a lot like an Otto Link Master Link mouthpiece. Otto Link and the Meyer Bros. worked very close to each other on many projects, and this is probably one of them.