Folded filter papers are somewhat thicker than Grade No. 1. Supplied in prepleated (folded) form. Surface is smooth with normal hardness. Medium crystalline precipitates, 8 µm, are retained. ASTM initial filtration speed is 55 seconds. Normal loading capacity. 0.7 mg of ash content per 12.5 cm circle. (For cost savings, see Ahlstrom equivalent, 447-300-02 Series)