The multi-disc pig, or multi-disc brush pig, is a bidirectional model equipped with four sealing discs and two guide discs. The guides support the pig’s weight but generally do not make full contact with the pipe wall under normal conditions. The sealing discs provide propulsion and sealing. Optional spring-loaded brushes improve cleaning and help keep the pig centered. These pigs are commonly used offshore because they can be reversed. They are also used for filling and dewatering because they seal effectively and remove water after hydrostatic testing. They may remain in the pipeline during the test and then be reversed back to their starting point. Custom features are available.