11.7mm - Calamine larger in the hand - same peak performance. A true 11.7mm diameter with an energy absorbing nylon core. Calamine CE is ideally suited for climbing sytems that require EN 1891 Type A certified climbing lines, such as the Petzl Zigzag. The nylon core produces slightly more bounce than Blue Moon. The 11.7mm construction makes it ideal for both SRS and MRS climbing systems.