Personalized I Believe In Santa 2 Youth Long Sleeve T-Shirt. Funny Christmas Youth Long Sleeve T-Shirt - Red with Santa cap says I BELIEVE IN SANTA... JUST BECLAUS. Perfect holiday gift for anyone who believes in Santa Claus and Christmas. youth long sleeve t-shirt. Shoulder-to-shoulder taping. Youth: S(6/8), M(10/12), L(14/16), XL(18/20)