Whatman 934-AH. The fine particle retention (1.5 µm) and flow rate (13.0 mL/sec) of this popular grade is superior for its high retention efficiency at high flow rates and its high loading capacity. This filter is a smooth surface, high retention borosilicate glass microfiber which withstands temperatures over 500°C. Specified in Standard Methods 2540D for determining total suspended solids in water, removal of turbidity and filtration of bacterial cultures. Grade 934-AH is used for a wide range of laboratory applications.