A pipeline pig is disclosed, the preferred embodiment incorporating all plastic components including a central elongate mandrel being hollow along the middle to a forward transverse partition, a nut which threads to the forward end of said mandrel, said nut and mandrel locking together to secure components on said mandrel. The device further supports N cups, the cups preferably backed by adjacent discs for stiffening purposes and being spaced along the mandrel by spacer means. Scrapper discs can be used with the leading disc being harder & smaller while scrapping discs are softer and larger.