My daughter wore this when she was 18. Unfortunately, there's no tag. However, she always wore adult small in her dance costumes, so I'm guessing that's what this is. The shoulder straps are adjustable. 

This gorgeous ballet dance dress with tutu is perfect for any Swan Lake performance or dance recital. The red and black color combination is stunning and will make any ballerina feel confident and beautiful on stage. Designed for women, this dress comes in adult small size and is made with high-quality materials to ensure comfort and durability throughout the performance. The dress includes a tutu, adding an elegant touch to the overall look. The dress is suitable for adult dancewear, specifically designed for ballet performances. Its excellent quality and design make it an ideal option for dancers who want to look their best on stage.