Personalized Superhero 1st Birthday Women's V-Neck T-Shirt. Happy 1st birthday! Celebrate your baby's first b-day with this cute I'm 1 superhero design. Happy Birthday one-year-old! 5.0 oz., 100% pre-shrunk cotton Athletic Heather is 90/10 cotton/polyester 1x1 rib collar with mitered v-neck Shoulder-to-shoulder taping Ladies' fit