This is a hardly-used Yamaha alto trombone in Eb, in outstanding condition.  It's the Custom (professional) top of the range model, and comes with a Vincent Bach 12C mouthpiece, which seems an ideal match (though others will have their own opinions about that). I bought it some time ago, but have hardly ever had occasion to use it and am cutting down on the number of instruments lying idle about the place - hence the sale.