We have an older Eureka Mighty Mite 3685 that has a hepa filter attached to the exhaust at the rear of the vacuum. It has lasted a long long time and has had many broken pieces that I have been gluing to keep it running. It is time to replace it. I have noticed that there is a model 3670 that looks very similiar. But it does not have the hepa attached at the rear. Does any one know if the hepa 60666B filter will snap onto the rear like on the 3685? None of the 3670 are shown with the hepa attached like the 3685 is.