Eyeing the MP7 PolarStar Jack Drop-In Kit available at Airsoftjunkiez from Bingo Airsoft Designs? Here is a demonstration video from Airsoft Junkiez to give you an idea on how to install it... "Detailed breakdown and install video of the Bingo/Airsoftjunkiez drop in PolarStar Jack Kit. Converts your TM MP7 or Well R4 MP7 into HPA. Overall look at the Chassis and all the components for easier install."