Teflon
judging by your profile pics, you'd need teflon for someone to slide that thing down their throat!
I've never had anyone take it all the way down either. It's sort of a dream of mine though, I've put up with lots of gagging, but then they quit. Once had a gal puke in the garbage can by the bed while trying to throat me. That sort of put an end to the moment.
I still get real hard when I see a vid of someone getting thier big one taken all the way down to the pubes. And have had many wet dreams about it. I don't think I'd last long if/when it ever happens.