Like many I've carried a neutral gray or grey card into the field with me for years. However, the old Kodak 18% card is about done for and I started looking on line for a decent replacement that is somewhat "weatherproof" if not totally "waterproof". In searching on line with a large variety of vendors there seems to be a lot of products offered up as 18% gray, but immediately followed up with statements of confusion and product reviews of more or less 12% gray and or used for white balance too. Say what? Is it a true 18% or not? So, I'm looking for a product that is say 4x6 inch card, weatherproof, and must be considered 18% or neutral gray. Specific product names or direct links would be of help.......thank you!