Our 3" (8 cm) precisely-machined, lace tips are made of surgical stainless steel. Sizes US000 1.5mm) ? US3 (3.25mm) are solid, have a tightening hole and MINI diameter join. Sizes US4 (3.5mm) ? US8 (5mm) are hollow and have a [S] diameter join. The size is laser imprinted on each tip. These TWIST tips can be used with any of our SPIN nylon cables or TWIST cables 6" (15cm) and longer.