A forged wheel is manufactured from a billet, or a large square piece of solid metal. The billet is heated to extreme temperatures and pressurized to take its shape. This thermal cycle process causes forged wheels to be stronger than cast wheels due to grain refinement. Consistent forging makes for stronger structural integrity with less material compared to a cast wheel, however the process costs more, rendering forged wheels the more expensive option. http://www.sxforging.com/forged-wheel/