Filter pads are classed in three categories as high throughput, clarifying, and sterile pads. High throughput pads are generally thick and work by in-depth action. They often contain diatoms, which loosen the contexture and increase the internal surface of the filter bed. They have high filtration flow, low clogging tendencies, and good retaining power for the particles. These are used as a first filtration of wines thick with colloids. They prepare the way for clarifying filter pads. Filter pads start working by adsorption, then the particles withheld close up the ducts and they work more by the action of sieving, their flow is therefore abruptly reduced and finally stopped.