Guarder SP90 AEG Tune Up Spring

The Guarder SP90 AEG Tune Up Spring is specially developed for AEG (Electric) airsoft replicas and can serve as an upgrade compared to the standard spring.

We regularly get the question which spring gives which fps / joule which is very difficult to estimate because it depends not only on the spring what this value will be after placing the spring. The air seal of the cylinder, piston, piston head and nozzle also have a large share in this.