From the ChiaoGoo website:
TWIST cables are memory-free! They consist of a multi-strand, steel cable coated with red nylon. Lifeline holes can be found at each end of these cables. Insert the T-shaped tightening key into the lifeline hole to assist with securing your tip/cable connection. SPIN tips will work with TWIST cables. Available in small [S], large [L] and MINI diameters.