Personalized 13th Birthday Party Gift T-Shirt. 13th Birthday Party T-Shirt - White has a unique and colorful balloon and stars logo in rainbow lettering with Party - 13 Rocks bday slogan. Get ready to celebrate in style. 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.