I bought this kit on Amazon. It's a spray-on super hydrophobic coating. I had hoped it would prevent water droplets from adhering to the surface of aluminum as I'm trying to divert any water from the rain gutter to some (yet to be determined) other location. It works fantastic! After coating this sample, it can be completely dunked in water and come out dry. So, for the geometry of the rain gutter water exit, I'll just go with the one that performed best, and use it in conjunction with this coating...a combo which should be more than sufficient.