Designed to work with ropes from 8-12 mm, the Lift ascenders have a comfy handle and a locking design that prevents the ascender from accidentally coming off the rope. Kong's chest ascender is designed to fit tight against your body for rope climbing efficiency. Hand weight: 225 grams|Chest weight: 160 grams|Rope Diameter: 8 mm-13 mm|CEEN567 and UIAA Certified