Personalized Monkey 1st Birthday 1 Year Old Girl T-Shirt. Cute Monkey T-Shirt - White for a 1st birthday has I'm One slogan. Cute gift idea for a one year old girl. 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.