Personalized Baby's 1st Birthday Polka Dot T-Shirt. Baby's 1st Birthday T-Shirt - Tie Dye Pink has cute baby wearing a polka dot birthday party hat. 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.