Universal Spring Shims are used to alter the power of your AEG according to how much power you are looking for. 

The shims are designed to slide onto the spring guide inside the gearbox to create tension in the existing spring. The more shims the more tension and more power. 

4 shims of various sizes are included to fine-tune to the desired power you require. 

Shim 1 - Increase by 5 FPS

Shim 2 - Increase by 10 FPS

Shim 3 - Increase by 15 FPS

Shim 4 -  Increase by 20 FPS

The shims are designed to be of various sizes that can be combined to tailor the FPS output.

Please adhere to the power (Joules/FPS) of your local laws and game site. Test incrementally how many shims you need for the required power required.