Yes Richard V6 is spot on, that rubber gloop is a nightmare to clean up even if you can get a fitter to remove the tyre when you tell him that you've used it! The sealing rubber on the internal side of a modern wire rim is soft and relatively fragile ( it seals the spoke nut ends from leaking air) and you really do need to treat it with respect. Also never tighten a spoke using a spoke spanner as this will tear it ,a also when removing a tyre, the tyre should be removed from the rear of the rim and not the outer wheel face as is traditionally the way fitters do it as the tyre can damage the seal as it is removed.
And like Richard I just wouldn't go near the stuff! It will only repair the smallest of damage and its not a fix, rather a get you out of danger or home if home is close!
Might consider using it if I was leaving Syria today and had a flat!
