High Accuracy Sub-Micron Intelligent Micrometer 0-25mm (0-1") Built in Wireless&USB Data Output, Resolution 0.0001mm (: Amazon.com: Industrial & Scientific
StonyLab Quantitative Filter Paper Circles, 46mm Diameter Cellulose Filter Paper with 20 Micron Particle Retention Medium Filtration Speed, Pack of 100: Amazon.com: Industrial & Scientific