Spiral wound gaskets consist of a mixture of metal and filler material. Generally, the gasket has a metal (usually high carbon or stainless steel) wound in a circular spiral outward (other shapes are possible), with the filler material (generally a flexible graphite) wound in the same way, but from the opposite side. This results in alternating layers of filler and metal. The filler in these gaskets acts as the sealing element, while the metal provides structural support. These gaskets have proven reliable in most applications and allow for lower clamping forces than solid gaskets, but at a higher cost.