I was using a home made setup with a XR's Only high-flow backfire screen & a TwinAir standard replacement filter. The XR's Only backfire screen scratched the inside of the air box up, and the stock replacement filter left a small space around the filters sealing surface. I never had an issue with the seal, but it's an eye-sore. I decided to order the actual TwinAir Power Flow Kit, and I am very happy. Only 40 buck from chaparral-racing.com. With the Twin Air cage, and the different foam construction, I think it will be even higher flowing, and has a solid seal around the entire filter. I recommend a Power Flow Kit for any dirt biker. (sorry to those who's kit is over 100 bucks).