2 layers of bright white or brown paper, punched, pleated, fitted with expansion straps, then glued together. For superior strength and longer working life.
White: 2 layers of bright white paper, punched, pleated, fitted with expansion straps, then glued together. For superior strength and longer working life.
HE: 2 layers of high grade paper, punched, pleated, fitted with a polyester final stage filtration, with expansion straps, then glued and stapled.