For tightening the join between your ChiaoGoo Interchangeable Needles (Sizes 2.75mm - 10mm) and Small or Large Cables.
Insert the key into the lifeline hole on the metal joins at the ends of the cables and and use as a handle to grasp and screw the connection. It is recommended to do this every time you attach your tips to a cable to make sure that the join is secure.
Each pack contains 4 keys.