Personalized So Cute Birthday Long Sleeve T-Shirt. Cute birthday Long Sleeve T-Shirt - White with colorful sprinkles and I'M SO CUTE IT MUST BE MY BIRTHDAY saying. For the birthday boy or girl. Pre-shrunk 100% cotton 6.1 ounce long sleeve t-shirt. Double-needle stitched neckline and sleeves. Quarter turned. Shoulder-to-shoulder taping. Adult: S, M, L, XL, 2XL, 3XL