Hi MN,
You may be referring to the new "Excel Fueler" also a Slimline product. I have not used one, but have seen them advertised. It has the threaded cap you mentioned. You can check it out here:
Hello,
> For my vent line I use a Slimline unit that essentially is a fitting
> with a pressed-in cap. On a recent maganize I recall seeing a
> different unit where the cap had an outer thread. This, I thought,
> made it easier to remove the cap. Anyway does anyone know who makes
> this fitting? Thanks in advance,
> MN