The 105 m/s FPS spring is calibrated in collaboration with Daniele Cimadoro of Terni Softair. The FPS spring is 100% Made in Italy and it is created in collaboration with leading companies in the sector. The material used is burnished and pre-hardened carbon steel wire with the addition of silicon and chromium EN10270 / 2. In the phase immediately following forming, the spring is stabilized in the oven at a temperature of 400 degrees centigrade for thirty minutes in order to optimize its duration over time. It is recommended to use the spring in association with spring guides and bearing piston heads to ensure maximum performance and durability. 100% MADE IN ITALY 100% COMPATIBLE MARUI