It was a standard caulking gun tube in the roofing section of my hardware store.
It's only been about 1.5 months since I sealed it up, but so far so good. It eliminated all the wind noise from the sunroof, which was a nice benefit although not the intent. We've had some snow and no leaks, but the real test will be this spring when we get some heavy rain to see how it holds up. From what I've read, though, this polyurethane is supposed to be the best stuff out there for this application. Silicone will attract dust, can get discolored, and can actually promote corrosion on metal.
It's not real pretty, but you can't see it unless you're like 7'-2". Ha!
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