Personalized Monster Truck 6th Birthday 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! 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.