Arsanus does a tutorial video to help you install the RA-Tech NPAs into WE Airsoft M9 Gas Blowback Pistol... "An In-Depth Tutorial on how to install a RA-Tech NPAS into your Gas-Blowback Pistol. This method should work on most Tokyo Marui/WE Gas Blowback Pistols and WE Open Bolt Rifles.

The Airsoft Pistol shown in the video is a 'WE-Tech Full Metal M9 Heavy Weight Airsoft GBB Pistol'.

If you would like to view the quicker, consolidated version click this link.

NPAS Stands for Negative Pressure Air System. It allows you to adjust how much gas goes through your GBB rifle/pistol to regulate your FPS if it's running higher than you prefer or higher than your fields limit."