Ahnu by Teva slip-on sandals with numentum technology. Men's Size 13. These sandals feature adjustable straps for maximum comfort, and a breathable synthetic upper material with foam insole for added cushioning. Excellent Condition With No Rips or Stains. From a smoke-free home. Numentum Technology is a neutral positioning system that is engineered to encourage the natural biomechanics of your foot in order to maximize the stability and efficiency of your stride, wherever it takes you.