They don't fit the stock air box. Some guys are simply removing the stock box, attaching the BHAF to the hose and laying in the right front corner. Ol Smokey has come up with a neat looking aluminum mount that goes in the same corner that holds the filter in place. The BHAF is supposted to let a lot more air into the engine without letting dirt into the engine as well as some folks fear with the K&N filters.
Do a search on this in the first gen section, sould find some additional info such as PN's etc.