I bought something curved like this from Pep Boys, it had a plastic area to hold, it was not all foam like this. The key is to put the Tire Gel on the Pad (first) and move the pad around the tire, fitting the curve of the pad with the curve of the tire... Doing it this way I NEVER spill any!
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I did not read any of the negative reviews, but I would surmise they are NOT using this application method...