Nike Free always helps enhance your body's natural motion, but the barefoot-like-running experiences vary from shoe to shoe. These variances are graded on the Free Scale. The lower the number, the more barefoot-like the shoe.

The numbering system indicates the cushioning of the shoe and follows a scale ranging from 0 (barefoot) to 10 (normal running shoe). Free 3.0 is the least and Free 7.0 (discontinued) is the most cushioned model so far.

It's lighter, more responsive and softer than previous versions. Embroidered eyestays around the laces help keep your feet secure. Pull tabs at the tongue and heel make for an easy one-hand entry.

To transplant the benefits of running naturally to concrete or asphalt, Nike's designers re-invented the way athletic shoes were designed, engineered and manufactured. The launch of Nike Free in 2004 ushered a series of ground-breaking innovations into footwear design.