ASG Ultimate Upgrade Springs are made from military grade steel for the best possible performance. The use of SiCr steel allows Ultimate Springs to provide maximum power and consistency with every shot. Tightly wound and ground spring ends and progressive winding ensure that the Ultimate Spring is correctly aligned and consistently compressed regardless of the rate of fire in the AEG. Each Ultimate Spring has been rigorously tested and pre-compressed to minimize power loss from initial compression. Each ASG Ultimate Spring has a convenient color-coded end so you can see at a glance which power level has been selected. The nominal spring strength number indicates the expected value in meters per second with ammunition weighing 0.20g.