Personalized Monster Truck 6th Birthday Youth T-Shirt. Monster truck 6th birthday! A monster truck drives through the frosting on a cupcake, splashing it around in a giant mess. Cool gift for the birthday kid! 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.