CdyBox 50KN Outdoor Rock Climbing Big 8 Rescue Descender Material: Aluminium and Magnesium alloy forging Measurements: Length 17cm, Width 17cm Rally: 50KN or 11023LB; Handles ropes from 8mm to 13mm. In high angle work and rescue, you need an 8 that you can tie off quickly and easily. The Kong Rescue 8 is a great mix of strength, weight and performance.