Originally Posted by Kokanee
You don't want a metal propane adapter; more prone to damaging GBB/GBBR fill valves. Check out a good polymer one from Airsoft Innovations at any nearby airsoft retailer.
OP asked for one with an oil reservoir. AI doesn't make one with an reservoir.
The metal adapters are fine. Even though I have a plastic AI one, that I take ti games, I also have their metal one and none of my fill valves have damage.
Now, the madbull one being stainless steel vs. the original brass AI one will be harder but still, if you use it right, it'll be fine.