Personalized I'm A Triathlete T-Shirt. Triathlon athlete T-Shirt - White for the competitor in your life who enjoys biking, swimming and running says I'm A Triathlete. Perfect for that next competition. 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.