Swift stack spring adapters are made out of a lightweight and durable composite material. It is made for racers that are looking to stack either a Helper or Assist spring onto the main spring. The stack spring adapter can also be use for racers that are looking to run two main spring (dual rate and progressive rate) type setup. The composite materials that are used on these adapters do not harm the shock thread. It also does not add to the un-sprung weight due to its light weighted composite materials.