The CK cups will only fit CK collet bodies, the CK collet bodies are the same fitment as 'Weldcraft' which has become a bit like Hoovers in that most torches are Weldcraft style i.e. a CK17, WP17, SR17 and a whole bunch of others are all 3/8 UNEF thread (along with 18 and 26 sizes) with 9/20 sizes using a 5/16 UNF. CK wedge collets are interchangable with the Weldcraft style. Clear cups don't stay clear for ever and are (or used to be, not used the CK ones) fragile compared to the pink alumina ones.