Newton's Performance Racer is the ultimate shoe for natural running. Engineered for speed, distance and performance. With a level platform construction and Action/Reaction Technology™, this lightweight, high mileage racer is the ultimate "PR in a box." Independent studies prove this technology, in conjunction with a natural running technique (see our ChiRunning page for more details), provides less stress on a runner's joints, muscles and tendons. SIZING: See Proper Foot Placement in Newtons page for important sizing information Please order your typical athletic shoe size. For runners currently wearing prior year Newton models, please order a half size SMALLER than your current Newton size. The ball of your foot must be over the middle of the lugs in order for the technology to work properly. This should result in about a thumb's width between the end of your longest toe and the end of the shoe. Call the store at 413-727-3188 if you need assistance deciding on a size - we're happy to help and can give you an accurate sizing recommendation based on your foot measurements.