These plungers, sometimes known as suction plungers, are made of plastic and have a concertina construction. This allows a much larger volume of air or water displacement and is the most effective way of removing a blockage. For maximum effect ensure the bellows are at least half full with water. Use a back and forth motion to push and pull the blockage. With a tight seal the backwards motion will actually suck the water away from the blockage. For very heavy blockages this is necessary in order to break it up and let the full impact of the force push it away.