Personalized 100 Days Of School 100 Days Of Cool T-Shirt. Our 100 Days Of Cool design features a playful and vibrant design that will bring a smile to anyone's face. Whether you're a student, teacher, or parent, this apparel is a fun and stylish way to commemorate the 100th day of school. 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.