Made of Silicon Chrome Steel & by machine.
# Variable Pitches so really smooth action.
# FAT Dia.(no available to original SP Guide)
We got a result to reach 400 FPS with TM L96 original inner Barrel & chamber,PDI Precision cylinderr set HD and 0.2g BB.
Please note :
This spring is over Toy spec,so your gun may get a fatal damage even though your rifle was tuned up.