Personalized Race Car 4th Birthday T-Shirt. Race car 4th birthday T-Shirt - Light Blue with red race car, checkered flags and big number 4. Side of car says BIRTHDAY CHAMP. 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.