Pack of 3x 5-micron Sediment Filters The Sediment filter is usually the first stage in a water filtration system. It serves to remove visible dirt particles such as mud, rust, and sand from the water. A Melted-spray filter cartridge has a multi-layer structure and is self-bonded, thus not making use of a chemical binder. After passing through this filter, the water may appear to be clean. However, looks can be deceiving and most water contaminants are smaller than what our eyes can see. These contaminants may not be removable by the sole use of a sediment filter. Sediment filters are rated by a micron number. A micron is a unit of length that is equal to one millionth (10-6) of a meter. The most common sediment filters available are 1, 5, 10, 20, 30, 50 and 100um (micron) filters. The micron number refers to the largest dirt particle that will pass through the filter. What's in the box 3x 20 inch Big Blue (20x4.5" size) 5-micron Melt Blown Sediment Filters