I don’t know what rating it is. It was the most porous thing that I saw on the rack there. All I know is I put it on my bike, and I’ve had three pair so far. Because of course, they wear out sometimes, or I just want to make a new pair and have them clean looking. I’ve got 24,000 miles on the bike and I’ve had the filters in there since about 3000 miles. I went for trips up to 4200 miles in the middle of summer in 105° weather pulling a Leesure Lite Camper Trailer, and it’s never moved off the middle of the temperature gauge. It only kicks the fan on when it needs to, just like normal. In fact, one of the pictures you can see the light shining through this stuff, so it’s very porous. It’s just enough to keep all the bugs out and when you take it out to clean, all you have to do is vacuum out the bottom of the area where the radiators are. Right at the bottom, some of the road crap and bugs collector there. Like I said, I take them and paint them black, wait for it to dry, and put them back in. And I wedge a half a coat hanger wire (from the bottom of the coat hanger) in there, and it works just fine to hold it in if you happen to make it too small. One side is like a pattern to hold the material on, and the other side is just porous material. Thing works great no problems ever. If it doesn’t work for you or you don’t like it, you only wasted 15 bucks at the most, and 30 minutes of farting around with it. It’s all good! lol