Personalized Mechanical Engineering Genius T-Shirt. Mechanical engineering genius with a line of gears is a unique gift design with attitude for engineers and students at back to school, birthdays, holiday and graduation. 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.