From Woburn Startup Extrudes Diesel Filters Like Pasta; The Way to Cleaner Cars?:

GEO2's microfiber filter, electronic microscope view
GEO2’s microfiber filter, electronic microscope view

On a microscopic scale, GEO2’s microfiber-based ceramic filter material (left panel) is like a stack of sticks, bonded by a glassy glue. The other two panels show filters made from more conventional clay-like ceramics. As can be seen, there’s more air space in the GEO2 filter—creating less backpressure for a vehicle’s engine to work against.