Personalized Cupcake Polka Dots 1st birthday T-Shirt. Whether you're hosting a birthday party or just want to dress up your little one for their special day, this 1st birthday outfit is sure to make memories that will last a lifetime. 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.