95 m/s FPS spring has been calibrated on 363 mm inner barrel and gearbox with type D cylinder (for barrels from 301 to 400 mm). Of course with shorter or longer barrel the performance will decrease or increase, therefore the calibration will be harder or softer. In the calibration process has not been taken in consideration the thickness due to the bearings of the spring guide and of the piston head. So starting by equal initial conditions you have to take into account of a performance increase of about 2.5 m/s for each bearing. The FPS spring is 100% Made in Italy and it is produced in collaboration with leading companies in the sector. The material used is steel wire burnished and pre-hardened carbon steel with addition of silicon and chromium EN10270 / 2. In the phase immediately subsequent to forming the spring is stabilized in the oven at a temperature of 400 degrees celsius for thirty minutes in order to improve the durability. The spring has coils with variable pitch in the central area and in that in contact with the spring guide and undergoes a process of grinding the two ends which guarantees optimal performance in the compression phase. The dimensions of the product are: - length: 170 mm - outside diameter: 14.30 mm Is recommended the use of the spring in combination with ball bearing spring guide and ball bearing AEG piston heads to ensure maximum performance and durability.