Personalized Birthday Stamp 21 Long Sleeve T-Shirt. 21st birthday Long Sleeve T-Shirt - White with distressed canceled postage stamp with fun birthday cake and number 21. 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