ASG Ultimate Upgrade Springs are made from military grade steel for the best possible performance. The use of SiCr steel allows Ultimate Springs to offer maximum power and consistency with every shot. Tightly coiled and ground spring ends and progressive coiling ensure the Ultimate Springs are properly aligned and consistently compressed regardless of 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 number of the spring strength quantifies the expected value in meters per second with 0.20g heavy ammunition.