Wix:  33110
NAPA: 3110

According to information in other forums, these fit the early models that have the filter out the side, but not the newer design that comes out the front.  Not sure if that is true.

Other sources also state the breather elements are no longer available, but some claim they have been able to "clean-up" the original "wood" type (which I have).  I'll give it a shot.