Ultimate comfort is the key benefit of this running shoe. With this 4th edition we improved materials to deliver that extra level of comfort and cushioning to keep you going longer. The platform consists of a large volume of Quikfoam and Quikspring foams, delivering a very comfortable, well cushioned running experience. Because of the unique geometry, the platform provides a very smooth and natural ride. The upper of the Spire 4 features a flexible engineered knit which is accompanied by the Morphit support system which secures a perfect fit around the midfoot. The pressure free tongue and Ortholite insole further help the shoe deliver ultimate comfort.