Zigzag filter media and frame having triangular pleat stabilizing elements

A zigzag filter comprising a zigzag pleated filter media and a filter frame, said filter frame having two continuous outer sidewalls and two inner sidewalls each of said inner and outer sidewalls are separated by a continuous fluid impermeable spacer element, the inner sidewalls having a plurality of upstanding triangular pleat stabilizing elements with first pleat stabilizing element sidewalls tapering outward from a peak toward second pleat stabilizing element sidewall segments, two adjacent second sidewalls segments on separate pleat stabilizing elements forming pleat tip retaining gaps, the pleat stabilizing elements having a shape such that the pleat stabilizing elements support and engage the zigzag filter media first pleat tips on a first face of the pleated filter media, second pleat tips being frictionally engaged by the pleat retaining gaps on said first face of the pleated filter media such that the filter media second face pleat tips are partially compressed in said pleat tip retaining gaps, said continuous fluid impermeable spacer element being downstream of said pleat tip retaining gaps.