CAMP TETHYS PRO SMALL MOBILE PULLEY. An ultra slim, highly functional pulley. The attachment hole allows full rotation of the carabiner. For ropes up to 13 mm. Prusik minding, the self-locking knot can be installed on one side. Sealed ball bearings for high efficiency and intensive use at high speed. Efficiency: 92%. Aluminum alloy body and wheel, stainless steel axle.