Here's Chiinnature/Mak Hobby showing you how to save on costs by using HPA to launch airsoft grenade shells... "Save all your Co2 and Green Gas money, go with HPA to charge your airsoft grenade launcher shells! With a Madbull Co2 Charger, you can now take the regulator off and hook it up as inline setup to your HPA tank and a filling adapter head, and now you can fill your grenade shells with HPA instead! Shoot all you want, it's free air you can pump back at home!"