Similar in principle to the cartridge filter, by virtue of being used until full of collected solids and then cleaned or discarded, are the small in-line capsule filters, much used in laboratories and the small-scale production processes of the lifescience industries. These are made entirely, both housing and filter medium, of a polymer suitable to the operating conditions. They take the form of short cylindrical housings (with a length of the same order as the diameter), closed at each end, except for a nipple or nozzle that can be connected to a plastic flow line. The capsule is inserted into the flow line, the process is run and then the filter is removed and discarded if it was removing contaminants, or its solid contents recovered if they are valuable.