Fast, clean & non-destructive "crack jumars" fit thin cracks, grooves and flares from 1/8" to 1 1/2". Clip a couple CAM HOOKS to each aider and shuttle up cracks with speed and efficiency, stopping occasionally to place lead pro. Amazingly secure, each CAM HOOK can be used in any width crack that will accept it - with varying leverage forces. CAM HOOKS work by multiplying your body weight via by the lever arm to increase the "bite" of the tip - which is subtlety tapered and flattened. Choose size (and also therefore leverage) appropriate for hard or soft rock... or fragile flakes (that could be damaged by a piton, SLCD, nut or chock that generate more force when loaded). Practice on top rope or low to the ground to get the used to CAM HOOKS capabilities, limitations and unique sound - which indicates they are working! Double up on Narrow & Wide sizes for most trade routes. Ask for us to sew on a compact color coded 12 mm Ultratape loop (maximum strength, durability and neat racking) or add 2 ft of 1/2 tubular tie off web to your order - jamming the knot on the outside of the radius. Based on original design of Ed Leeper, Micro-Wide are 4130 chromoly steel, Extra wide FRAGILE FLAKE is high strength aluminum alloy and imparts the lowest force. Recommended weight limit 250 lbs / 550 kg. Made in California.