Since it comes from Vittoria, I assume that they have formulated the goop to get past a Presta valve. That has been a problem with other goops sold in the past. The thing with goops is that if it doesn't work, for whatever reason, you now have an unholy mess in your tire and rim. Further repairs can be a bit diffficult. Plus, you are now in the middle of frick-all nowhere in a downpour without a method of repair and inflation. If I were doing clinchers, I would prefer one spare tube and a patch kit. If I were doing tubulars, I might consider this....but I would rather carry a spare tubular and repair the busted one at my leasure. I guess I am a skeptic. Let us know how it goes......