You don't really NEED one, but it's definitely a good idea. If dirt or stones get down that tube it'll drop into your transmission, and that's never a good thing. I got my UNI breather at the local powersports shop for $15, or you can go to the auto parts store and find one that fits the breather hose. Just take the hose along with you to your favorite auto parts store, and tell them you need a breather filter that fits it. It'll probably cost a little less than my UNI breather did, and it does the same thing.