pro-flow with k&n vs k&n alone- confused

[okc400]

I have a fully stock '03 kfx 400. I'm in the process of doing the "big 3" mods- full pipe, intake, jet kit. I purchased a full Yoshi exhaust off the internet and the jet kit at my local retailer. When I asked about a K&n filter my retailer asked if I wanted "just the K&N or the pro-flow kit?" The pro-flow is more expensive. I do plan to run with the airbox lid off but I really don't understand the difference between a straight K&N and a K&N with pro-flow. Could someone explain the difference? Do I need the pro-flow?
Thanks in advance,

okc400
riding the plains of Oklahoma

[zracer16]

The Pro-Flow Kit comes with an adapter that you install on your airbox to mount the filter. It changes it to a clamp-on style air filter as opposed to the crappy way the stock one mounts. The Pro-Flow will add more air flow which mean more power. I would get the Pro-Flow because it A. Adds more power and B. The way the filter mounts is much better than stock.

[okc400]

Thank you for the clarification. Sounds like I better spend the extra money and get the pro-flow.