Or Fuel Lube. I bought a can, which is probably a lifetime supply and then some. It has the consistency of earwax, which is what the friend who used it to help seal the lines passing through his firewall in a Lancair PropJet calls it. I used it on NPT fittings and the screws for sender and inspection plate on my tanks (as well as a thin coat on the cork). DON'T use it on engine fittings (Superior recommended another sealant, which escapes my memory right now, but is intended for high heat applications). I think ACS is selling the stuff again but a can is many times too much for a single project; see if you can find a local A&P or builder who can supply you with what they have instead of getting a whole can for yourself.