All panel filters of MS are constructed with enclosure frames made of two die-cut pieces of heavy duty Beverage Board bonded together to form a double wall. It is treated with moisture resistant additive to prevent collapse during high humidity. The support members of the enclosure frame are bonded to the media and gird combination to maintain correct pleat spacing. Air filter performance is measured by dusting holding capacity and filtration efficiency. Greater dust holdings capacity efficiency means longer service life and lower operating costs. Greater efficiency means cleaner air and reduced maintenance costs.