The Fann Model 90 Dynamic HPHT® filtration system utilizes special Filter Cores designed by Fann engineers for conducting filter cake formation and permeability analysis. The filter medium is a thick-walled cylinder with rock-like characteristics to simulate the build-up of filter cake on the formation thus providing more accurate filtration measurements. The entire internal length is subjected to pressurized fluid (sample). Filtrate flows through the core radially from the inside to the outside. The filter medium is available in varying porosities and permeabilities to simulate down-hole formations.