Tried to use this to patch an AC return line in a car. Didn't want to take the line out, so figured it would be worth a try. It was a vertical line, so was more difficult. Tried like 4 times to get it to seal the leak. Never would. So I ended up cutting and splicing the line with a coupler instead. Was worth a try, if it would have worked out it would have been a cheap easy fix, but no go.