Personalized Mermaid Princess 6th Birthday Long Sleeve T-Shirt. 6th birthday Long Sleeve T-Shirt - White with a beautiful little mermaid princess wearing a crown atop her red flowing hair and surrounded by cute fish and starfish. Text says THIS LITTLE PRINCESS IS 6. Pre-shrunk 100% cotton 6.1 ounce long sleeve t-shirt. Double-needle stitched neckline and sleeves. Quarter turned. Shoulder-to-shoulder taping. Adult: S, M, L, XL, 2XL, 3XL