Whatman 1001-032 Quantitative Filter Paper Circles, 11 Micron, 10.5 s/100mL/sq inch Flow Rate, Grade 1, 32mm Diameter (Pack of 100) B00394F96Y. $47.33 $23.39. Features: 3.2cmGrade 1Covers a wide range of laboratory applications; frequently used for clarifying liquidsAreas of use include the food industry, agriculture, air pollution monitoring