Merrell Siren Nitro has uppers constructed from full grain pigskin/suede leather and canvas uppers. Just the job when the going gets rough and you need built in ruggedness, the Merrell Siren Nitro has tough Vibram Siren trademarked rubber sole giving superb shock absorbing stability and steady traction for uncertain terrain. The footframe is moulded from triple-density compression moulded EVA material, the antimicrobial polyester mesh lining is breathable and the Merrell Siren Nitro footbed is anatomically designed to fit the foot. There is a built in injection moulded arch shank and this Merrell Siren Nitro midsole dynamic multi-functional shoe has an air cushion.