High quality spring 140% from Japanese PDI. Made from high-quality spring wire (chrome-silicon steel) with a blackened surface against corrosion. Material and the entire production process has been certified by the Japanese certification office, which means high quality and grade. Through proper adjustment can spring a long retains its characteristics (tested with >20 thousand fire and without change). Properly designed progression climb of winding allows little resistance during compression and a rapid return spring after release.

Japanese manufacturers mark their spring by percentage. This can be confusing , so approximate toughness of spring is M100 of standard marking.