TLG® Ashless Quantitative Filter Papers No.41 have very fast filtration speed and are typically used in air pollution analysis, soil pollution analysis, metals analysis after nitric acid digestion, gravimetric analysis, and preparation of samples for instrumental analysis. SPECIFICATIONS Material: High Quality Cotton Linters Porosity: Coarse Particle Retention in Liquid: 20-25µm Herzberg Filtration Speed: 68sec/100mL (or ASTM: 12sec) Nominal Thickness: 185 ± 10µm Nominal Weight: 92g/m² Nominal Ash Content : 0.007% Package Size: 100 Pieces