Personalized Trombone Rocks Newborn Layette. Trombone Rocks with three dancing rocks holding trombones is a humorous low brass design. Fun gifts for musicians at back to school, marching band, birthdays, holidays and graduation. 100% combed ringspun cotton 5.8 ounce 1×1 baby rib sleeper. 3/8" flatlock binding at envelope neck and cuffs. Back sleeve flap to protect hands. Elastic opening at bottom. Infant: 0-3 Months