Glass is designed to optimise solar energy conversion while providing long term protection against external conditions. Extra clear glass, with low iron oxide content is typically used in solar applications. Either float or patterned, low iron glass may be coated with an anti-reflecting coating to further increase performance. Transparent conductive coating can also be used as an electrical contact in some photovoltaic technologies allowing the light through to the photovoltaic material while conducting the general electricity out of the modules. Glass may also be toughened to increase strength and durability.