ChiaoGoo end stoppers are accessories for the "Twist" and "Spin" interchangeable needle sets. The end stoppers attach to the ends of the cables allowing you to safely "park" a project on a cable to use the needle tips on another cable and another project. They can also be used with a needle tip at one end of a cable and an end stopper at the other to create essentially a single-pointed needle with the capacity to hold an extremely large number of stitches. Be sure to purchase the correct size. The small, white end stoppers are for use with small cables, which fit needles size US 2 (2.75mm) through US 8 (5mm). The large, black end stoppers are for use with large cables, which fit needles size US 9 (5.5mm) through US 15 (10mm).