So I'm making an auxiliary fuel tank to fit in place of the left muffler on my 950 Adv. What to use for a filler has been a question. I could make a filler neck to fit a screw on Acerbis cap... or use a ready made aluminum neck and cap... or use a stock flip up filler cap assembly and have a nice locking cap. My tank has just enough room to bolt on the flip up cap assembly and if I extend the mounting flange just a bit I won't lose much capacity. If anyone has a spare cap assembly they would like to see go to a good home, please let me know. Hmmm, I suppose the lock cylinder is replaceable so I can key it to match my bike?