The Modify Irregular-Pitch Spring will allow your gun to shoot at a very consistent FPS.  It is as easy to install and also available in different models. If you install M170 or M190 spring, we suggest that you buy the Reinforced Spring Guide Stopper together for best result.

Specifications:

• For 9mm spring guide usage
• Suitable for Modify MOD24 Bolt Action Rifle, APS-2 and SSG24
• Material: High-grade piano wire