This is the strongest and longest spring and is uncut. Get this if you want to cut down the spring yourself for maximum Level 10 effect. This will push the level 10 effect to the limit at a significant efficiency loss. This spring is only available on its own and recommended for use by experienced user only. Some older marker models and pistons may not be able to shoot at all with this spring. This is also the main spring for the FN 303 which operates at a higher pressure and requires the stronger spring.