Personalized Baseball 8th Birthday T-Shirt. Baseball 8th birthday boy. Baseball league style with bats and varsity letters. Sports theme for your 8-year-old's b-day party. Happy Birthday eight-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.