Rocket Airsoft M170 AEG Spring

Rocket Airsoft M170 AEG Spring. Silver type upgrade spring that is non-linear. Fits in all gearboxes. The heaviest AEG spring type there is for common builds. FPS will be 550 or so. For heavy upgraded guns, DMR, etc only. Experienced techs only. (please note: packaging may be generic or labeled as 'Rocket Airsoft', but is made by SHS OEM) This spring is a total pain to install, so be forewarned.