I have one of the Huma fillers that is a great addition, allowing me to fill a couple of spare bottles. However, it did cause my older FX bottle to leak completely when I initially filled it with my Hill compressor. The adapter uses air pressure to force the valve open, this dislodged the valve seat. I disassembled the valve and put the valve seat back with a new tighter oring and all good. No problems with the newer FX bottles, so maybe they have an integrated valve seat. Note that this set screw is only used to empty a bottle.