Alloy wheels are automobile (car, motorcycle and truck) wheels which are made from an alloy of aluminum or magnesium. They are typically lighter for the same strength and provide better heat conduction and improved cosmetic appearance over steel wheels. The earliest light alloy wheels were made of magnesium alloys. Although they lost favor for common vehicles they remained popular through the 1960s albeit in very limited numbers. In the mid to late 1960s aluminum casting refinement finally started to allow manufacture of wheels that were safe. Until this time most aluminum wheels suffered from low ductility, usually ranging from 2-3% elongation. This meant these earlier aluminum alloy wheels were quite brittle, and as light alloy wheels at the time that were often made of magnesium and referred to as "mags" these early wheel failures were later attributed to magnesium's low ductility, when in many instances these wheels were poorly cast aluminum alloy wheels. Once these aluminum casting improvements were more widely adopted, the aluminum wheel took its place as low cost high performance wheels for motorsports.