Personalized 12th Birthday Party Gift Youth T-Shirt. 12th Birthday Party Youth T-Shirt - White has a unique and colorful balloon and stars logo in rainbow lettering with Party - 12 Rocks bday slogan. Get ready to celebrate in style. 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.