"The product certainly moulds and hardens as it should so full marks for that part. The problem as I have experienced is that the material has to entre the ear canal and harden. It’s this part of the structure that interrupts the sound and protects your hearing. Your ear has a narrowing then opens as it continues toward your ear's working parts. The mixed material passes through the restriction, no problem but it cannot expand to then fill the now open part of your canal and it is this bigger part that keeps the plug in place. I found that when I moved or opened my mouth when these plugs are in place that they move and break the close fit and from that point you get very little protection. I have had professionally made custom plugs made in the past and they have a definite expansion at the canal end. If you have hairy ears be sure to clip the hair very closely before moulding."