PTFE PM2.5 Air Monitoring Membrane Filter, 46.2mm with support ring, 2.0 um, 50 per pack, SF18040. Regular Price: $454.25. Price $336.00. As low as: $252.00. Add To Cart. 1. 2 items. Sort Best Sellers Grade Particle Retention Format Alphabetical Price: Lowest Price: Highest. View Grid List.