More effective on lighter targets are the expanding bullets, the hollow point bullet and the soft point bullet. These are designed to use the hydraulic pressure of muscle tissue to expand the bullet. The hollow point peels back into several connected pieces (sometimes referred to as petals due to their appearance) causing the bullet to create a larger area of permanent damage. The hollow point fills with body tissue and fluids on impact, then expands as the bullet continues to have matter pushed into it. This process is informally called mushrooming, as the ideal result is a shape that resembles a mushroom—a cylindrical base, topped with a wide surface where the tip of the bullet has peeled back to expose more area while traveling through a body. For the purposes of aerodynamic efficiency, due to the hollowpoint not creating drag, the tip of the hollowpoint will often be tipped with a pointed polymer 'nose' which may also aid in expansion by functioning as a piston upon impact pushing the hollow point open. A copper-plated hollowpoint loaded in a .44 Magnum, for example, with an original weight of 240 grains (15.55 g) and a diameter of 0.43 inch (11 mm) might mushroom on impact to form a rough circle with a diameter of 0.70 inch (18 mm) and a final weight of 239 grains (15.48 g). This is excellent performance; almost the entire weight is retained, and the frontal surface area increased 63%. Penetration of the hollowpoint would be less than half that of a similar nonexpanding bullet, and the resulting wound or permanent cavity would be much wider.