The Mammut Smart Belay Device locks at en extremely low force, so you can catch your friend"s massive whippers with ease. This unique belay device also works on anything from an 8.9 to a 10.5mm rope, so you"re not stuck with something that doesn"t work when you get to the crag. Product FeaturesAuto Locking: NoStrength:Rope Diameter: 8.9 - 10.5mmWeight: Recommended Use: Rock climbingManufacturer Warranty: 1 Year