Brooks Men's Pure Connect 3 mesh Lightweight uppers feature highly breathable polyester mesh and a rubber instep band to provide a comfortable, secure fit regardless of foot shape Ideal Heel design uses a curved heel to encourage foot contact points to shift you forward, helping to align joints and reduce stresses 4mm heel-to-toe drop encourages a natural midfoot or forefoot strike to promote forward momentum and reduce the impact of heel striking Split toe groove under the forefoot enables the big toe to function independently and helps encourage natural balance