Personalized Baseball 8th Birthday Youth Long Sleeve 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! youth long sleeve t-shirt. Shoulder-to-shoulder taping. Youth: S(6/8), M(10/12), L(14/16), XL(18/20)