DECOY WH-02 Decoy Worm Holder/Spring Type; Size: M/4.0 mm; L/5.0 mm; Quantity: 4 pieces; Simply reduces the amount of slacks. Eco friendly and quick return! A normal rig will cause worms to run out because the force is concentrated at one point where the hook is sticked. But by screwing this spring into the worm and setting the hook so that it is hooked on it to disperse the force on the worm and it greatly reduces the amount of breakage. It does not waste worms, so it is also an eco-friendly item.