The next step in climbing rope technology, the Sterling Evolution Duetto Dry AT Rope boasts all the right credentials to help you up your alpine project. With a slim 8. 4mm profile but just the right amount of stiffness, the Evolution Duetto slides through "biners like butter and all but eliminates your rope drag concerns. A low impact force rating of 6. 5 kN indicates minimal stresses during even your more dicey lead falls.