Personalized 4th Birthday Rocks 4 Year Old Girl Youth T-Shirt. 4th Birthday Youth T-Shirt - White have plaid heart design number four with princess crown and 4 Rocks quote. Let the good times roll in a durable T-Shirt that takes kids from school to play in an amazing array of colors. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar.