PETZL Croll chest ascender Used with the ASCENSION rope clamp for ascending a rope, the toothed cam with self-cleaning slot optimizes performance under any conditions (e.g. frozen or dirty ropes.) Thumb catch can be pinched for easy manipulation when the clamp is in position, and the angled attachment hole allows the device to lie flat against the chest. Weight: 130 g Rope diameter: Single ropes, 8 - 13 mm