Personalized Baseball 7th Birthday T-Shirt. Happy 7th birthday! Celebrate your child's seventh b-day with a cool SUPER 7, superhero personalized gift. Customize and add your child's name. Happy Birthday seven-year-old! Everyone loves our Custom T-Shirts! 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.