Proteam 510184 dome filter is specially designed to fit Proteam SuperCoach Pro 6 and SuperCoach Pro 10 backpack vacums.  Unlike whimpy cheapy foam filter that fail to trap dangerous invisible airborne particulates . . . this dome filter gets it done.  What's your health worth?  Top Choice:  Universities, Hospitals, Schools, Day Care, Offices, Resorts & Hotels, Churches, Airports, Theaters, Stadiums, Fitness Centers, Government, Military, etc.  If you're the one vacuming a lot during the day . . . you want to make sure you're changing the dome filter every 60 days (30 days if dirt load is heavy).  When your health and safety matters more . . . .