With its brand new Altra Quantic midsole foam, the Altra Superior 4.0 sheds some weight and gets back to its roots. The new upper is comprised of a seamless and stretchy toe-box, with a durable and supportive material in the midfoot and heel. Like the rest of Altra's trails shoes, the Superior 4.0 is equipped with the velcro gaiter attachment. To protect your feet from stone bruising, this model also includes a removable stone guard. Finally, the addition of sticky rubber on the outsole gives the superior 4.0 improved grip on slick surfaces allowing you to fly down the trail with confidence.