I had one of those airbox lids before on my 250R, and i really wasn't too impressed. I like the concept, but it cost too much money in my opinion. Money is better spent on a second airfilter and changing it mid day! I rather run an HRC lid as opposed to the EHS lid in muddy condition. I found that water WILL definately penetrate that outerwear. Actually what will happen with that lid is that water may not get through immdiately but instead, it will pool up ontop of the outerwear then come through down onto the filter, IMO a wet filter will hurt you more than a dirty or dusty filter! I agree with 86atc250r, the HRC lid will deflect most water from hitting your filter directly, some water can get into the airbox, where it will go into the drain tube. IMO a better solution than the EHS lid would be a combination of the HRC lid and a filter OuterWear. This combo will keep your filter very safe. The outerwear will deflect sand, dust, and most water away from the filter, down into the air box. I found that I had more power with a filter outerwear and a cut airbox, as opposed to running the EHS lid on my 250R, I have a feeling this would probably hold true with my 450R as well. The EHS lid would work ok in the sand dunes though where water is not an issue, but again, you are much better off with running an open airbox with an outerwear on your filter instead!