The Black DiamondATC(Air Traffic Controller) is a very slick belay device in use making it easy to pay out fat single ropes quickly when you leader isdynoingfor a jug. However the braking effect whenabseilingon skinny double ropes is nowhere near that of BD'sATC-XPand similar grooved belay plates and this is not really a device for beginners or those prone to dozing off on belays. This classic design features a large surface area that dissipates heat when lowering or rappelling, and the smooth-handling geometry accommodates rope sizes from 7.7 mm to 11 mm. Unique, smooth-handling geometry. Minimalist design is durable in all conditions. Large surface area dissipates heat when lowering orabseiling. Handles ropes from 7.7 to11mm- though better on fatter ropes. Weight (approx.): 60g.