Abstract: An improved corrugated sheet aluminum spacer for use in pleated media air filters is disclosed. The spacers are folded in zig zag fashion along one edge in a succession of V formations having a first height and width, and along the opposite edge in a succession of V formations having both heights and widths approximately one-fifth of the first height and width. Since the fold lines are substantially parallel, there are five V formations within a given width of the opposite edge for each one along the first edge, the fold lines of the intermediate V formations extending from the second edge only a portion of the distance to the first edge, but preferably about 90% of the length of the sheet. The V formations are formed by passing the aluminum between a pair of rolls with forming blades having overlapping edges which engage the sheet. The height or amplitude of the V formations at the small end is on the order of 0.03 to 0.04 inches in aluminum sheet having a thickness of 1 to 2 mils, preferably 0.0015 inches.