FPS 420-450 Madbull have brought out a range of colour-coded springs that perform just as well as it looks. The colour is actually hard-coated onto the springs via a special process, and is not painted on. Madbull have been testing these springs thoroughly and have proven that the length and force remain consistent throughout. Other features: Consistent even for 100000 shots! Non-linear design (calculated) Colour coating to reduce effects from environment Designed and Manufactured by experienced engineers. Premium quality German piano wire