OPTIMAL is designed to operate under normal conditions and is constructed to provide an excellent combination of low initial purchase price and superior performance. The enclosing frame for Optimal is a rigid, high wet strength, heavy duty beverage board. The frame and its integral supports are bonded to the media to insure pleat stability and air bypass. A metal grid on the air leaving side supports the media. The grid provides extra strength and helps maintain the proper pleated configuration through the life of the filter