That the beauty of it Clive, is that you can re-use it, it's not just a get you home measure. On top of that ultraseal conditions the tyre so that it doesn't deteriorate the as much when your 'vans laid up for a while. It also encourages lower tyre temperatures when on the move, and if you are unfortunate to have a tyre fail ultraseal will reduce the decompression rate to hopefully allow driver control.