Personalized 1st birthday T-Shirt. Make your baby girl's or baby boy's 1st birthday extra special with our adorable birthday outfits. Whether you're planning a big birthday bash or a small family gathering, our outfits will help create lasting memories of this milestone occasion. Shop now and make your little one's 1st birthday one to remember! 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.