FitFlop Vitamin FF eO1 Knit Sport Sneaker Biomechanically-engineered for exercise and casual running, the Vitamin FF eO1 is a pull-on sport sneaker with a comfortable, foot-hugging, wide elastic strap. Engineered to provide extra support at the sides and arch, you'll want to wear these stylish shoes for everything from speedwalking, to work or cylcling around town.