Working equally well for top roping or lead climbing, the Petzl Grigri 2 Belay device offers assisted braking and excellent descent control, and works with single ropes between 8.9-11 mm.. . . . . Designed to work with single ropes between 8.9 and 11 mm (optimized for ropes between 9.4 and 103 mm)-use it with your workhorse rope when top roping or use it with your skinny cord while working on your project. Assisted braking: during fall arrest, the belayer holds the brake side of the rope, the cam pivots and pinches the rope, increasing the braking action until the rope stops sliding. Stainless steel friction plate and cam ensure longevity. Progressive descent control system is designed to offer smooth, even lowering action-theres a larger "sweet spot" when lowering a climber or rappelling.