Production： Classification Grade Efficiency (%) Resistance (Pa) Tensile Strength Thickness (±0.02mm) Basic Weight (±4g/sqm) Stiffness (≥mg) MD (KN/m) ULPA U16 ≥99.9999 ≤580 1.0-1.25 0.34 75 950 U15 ≥99.999 ≤480 1.0-1.25 0.34 75 950 HEPA 0.3 mm @5.3cm/s H14 ≥99.995 ≤420 1.0-1.25 0.33 74 950 H13 ≥99.97 ≤330 0.9-1.20 0.33 74 900 H12 ≥99.8 ≤260 0.9-1.20 0.33 74 900 H11 ≥98 ≤180 0.9-1.20 0.33 74 900 H10 ≥94 ≤120 0.9-1.20 0.33 74 900 ASHRAE 0.4 mm @5.3cm/s F9 ≥95 ≤80 0.9-1.15 0.33 70 850 F8 ≥90 ≤60 0.9-1.15 0.33 70 850 F7 ≥80 ≤40 0.9-1.15 0.33 70 850 F6 ≥60 ≤25 0.9-1.15 0.33 70 850 Bag style: round bag (steel belt style) flat bag, special-shaped bag, drawstring bag, Filter bag head with thick felt, bottom reinforcement, bag body with iron ring,etc.