65mm ID Adapter kit comes with an adapter and 2 metal washer sheets (1 kit for 1 spring).
Swift Helper Springs are made from a proprietary material. Helper springs allow the spring to stay on mounted on the coilover perch when the shock is under negative or zero load, also known as droop travel.
The same springs are used in Super GT, Formula Nippon, F3, F3000, Super Taikyu, IMSA, Pirelli World Challenge, Rally America, VLN, Le Mans Series, Formula Drift, and many other professional racing avenues.