Donaldson® Ultradepth™ FF, MF, and SMF filter elements utilize a three-dimensional Ultrair™ microfiber fleece media, which is made out of glass fibers. An integrated 1 µm prefilter media provides two-stage filtration. In addition, this media will capture and retain liquid aerosols and solid particles down 0.01 µm through direct impaction, sieving and diffusion.