THE 9: Toehold | Hyperflex | Engineering This revolutionary new design delivers unprecedented durability and flexibility by reinforcing the most common high-stress areas of the shoe to help prevent wear and cracking. TOE HOLD OUTSOLE SYSTEM features an abrasion-resistant compound designed to resist toe drag breakdown, and two state of the art HYPERFLEX CHANNELS that allow the sole to flex and stretch freely, for exceptional comfort and unparalleled flexibility that extends the life of the shoe.