Coated foam pigs are available in light (1–2 lb/ft³), medium (5–7 lb/ft³), and heavy (8–10 lb/ft³) densities. They are standard cleaning models in the foam pig category. Medium density is standard in this category, while light- and heavy-density pigs are suited to specialized or challenging applications. The tough polyurethane jacket surrounding the pig extends its service life by dozens of miles and increases cleaning aggressiveness. Many operators prefer foam pigs because of their forgiving nature and extreme range of applications.