Lol, yeah I did take a little sidebar with the caterpillar! Hmmmm so the red cap is supposed to have a filet in it as well.. That could be part of my problem as well (or at least a major concern for the longevity and preventative maintenance), mine is just a cap and is missing the filter material or whatever should be in there to keep dirt out... In the illustration (The top portion of the third one) you see how the back is rather odd shaped but overall square? I'm guessing that is the housing for the diaphragm?