Personalized 3rd Birthday Polka Dot 3 Year Old T-Shirt. Happy 3rd birthday design has navy and white number 3 on a T-Shirt - White for girls turning three years old Wardrobe essential for looking good, 24/7. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar. Shoulder-to-shoulder taping. Double-needle stitched sleeves, bottom hem and front neck. Note: greys are a cotton/polyester blend.