A filter including alternating
layers of filter medium and
diffusion medium. The filter provides optimum distribution of fluid over the filtering medium, a reduced pressure drop and an increased filter life, without a reduction in filter rating. The
diffusion medium has a first plane of spaced-apart, substantially parallel strands defining first longitudinal passages having a first height dimension and a first width dimension, and a second plane of spaced-apart, substantially parallel strands defining second longitudinal passages having a second height dimension and a second width dimension. The strands of the second plane of the
diffusion medium are oriented in a non-parallel manner with respect to the strands of the first plane, such that the first and the second planes define lateral openings having side dimensions. The first and the second longitudinal passages include at least one dimension that is smaller than any of the side dimensions of the lateral openings. At least a portion of the
layers of filter medium have bypass apertures, wherein such portion defines at least one pre-qualifying filter medium layer.