wix makes them. i cut a new one open once, spread out the media and held it up to the light. you can actually see tiny holes (specs of light) in the media, when held up to a light. i have done this test to every new filter i have ever cut open and have never seen anything as bad as the protec was
That is interesting. I bought 2 cases of Pro-tec 101's for 80 cents/filter some time ago. I'm down to little less than 1 case and have noticed no ill effects. Then again, the cars I've used them on only get hundreds of miles per year.