The perfect killing machine! The Arch Flex provides an aggressive but comfortable fit that gives the shark an unparalleled level of performance. Built around the original Shark last, we?ve resurrected this old favorite providing new features to make this model the weapon of choice. By utilizing our 1.8mm R2 rand rubber, the Arch Flex system gives our redesigned Shark an unbelievably comfortable and glove-like fit. The elastic property in our R2 formula hugs and locks your foot in to place without the pain associated with other high performance shoes.