CK 7C20 0.5mm long lasting Reverse collet, For CK 17, 18 and 26 Tig torch, compatable with WP 17, 18 and 26 tig torch. The longest-lasting collet offered by CK Worldwide is the Reverse collet. This collet lasts longer than both the standard collet and wedge collet combined, due to its position in the torch head. It sits between the collet body and the backcap, keeping it away from the heat at the front end of the torch. It’s very small, easily replaceable, and cost effective. For 3 series tig torches.