Personalized Race Car 4th Birthday T-Shirt. Cute Race Car with the number 4 on it for your little boy's 4th Birthday is fun and colorful and comes on a party T-Shirt - White gift. art c. Ne' Metzger 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.