PWRRUN cushioning gives you springy energy return and plenty of durability. Extended medial post supports the bodys natural alignment with added guidance. More flexible TRI-FLEX outsole for a smoother run. FORMFIT hugs the foot in 3D comfort and delivers our most personalized fit yet. Engineered spacer mesh provides structure or stretch where needed and enhances breathability. A combo of iBR in the forefoot and XT-900 in the heel provides cushioning where you want it and durability where you need it. APMA Approved. With a lighter footprint, this style contains recycled materials.