It has nothing to do with the amount of product, so much as the size of the container you're carrying the stuff in. I got into a discussion with one of the TSA guys a month or two ago when I had decided to travel to the West Coast in civilian cloths. He found this clear plastic tube I had with my shampoo in it. The majority of the contents had been used and so there was maybe 1/5th of the original contents still left. The problem was that the TSA guy keyed on the fact that the tube was labeled as a 4 once tube. He said I couldn't take it because it was over 3 ounces. I said that, as he could plainly see, most of the stuff inside was gone. He said it didn't matter as the tube clearly said 4 ounces. I gave him my shampoo and continued on my way, shaking my head at the stupidity of it all.