Rubber sole The 4 is bringing back the super tough yet breathable mesh from the original version. The upper gets embellished with a Huarache-inspired strap and rubber-striped sidewall that envelops your heel to brace you for movement in any direction. Nike Free technology in the forefoot creates flexibility for agility moves and sprints. Stretch around the collar lets your foot move naturally as you burst, cut and brake The Nike Free Metcon 4 combines flexibility with stability to help you get the most out of your training program. Updated "chain-link" mesh cools and flexes as you speed through agility drills, while support at the midfoot and heel braces you for your heaviest sets in the weight room.