Personalized I'm One Derful T-Shirt. I'm One Derful! Pow! Wow! First birthday comic book style for your wonderful little superhero. Great 1st birthday present. Everyone loves our Custom T-Shirts! Wardrobe essential for looking good, 24/7. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar. Shoulder-to-shoulder taping. Double-needle stitched sleeves, bottom hem and front neck. Note: greys are a cotton/polyester blend.