Personalized T-Rex 1st Birthday Youth Long Sleeve T-Shirt. A cute little T-Rex dinosaur is smiling and wearing a birthday hat as it sits with its 1st birthday cake. Adorable gift for your one year old! youth long sleeve t-shirt. Shoulder-to-shoulder taping. Youth: S(6/8), M(10/12), L(14/16), XL(18/20)