SR25 Retro Arms SiCr spring with a progressive irregular coil M130

SR25 Retro Arms SiCr Spring with Progressive Irregular M130 Coil

Main spring made of chromium-silicon steel, for Long type gearboxes.
The progressive coil makes it easier to wind the spring without losing its power.
Spring dimensions:
Inner: 11.3 mm
Outer: 14.5 mm
Length: 185 mm