Heated towel rails are generally available in a choice of models, finishes and colours. Most models are available in either an epoxy or powder paint coating. Other options, depending on model, include chrome, gold-plate, and stainless steel. Heated towel rails are as a general rule available as independent electrically operated units or, for integration with central heating systems. In most cases these latter units may optionally also be fitted with electrical elements for use when the central heating system is switched off. Radiators or towel warmers that are fitted in bath and shower rooms are renowned for rusting and corrosion due to the extreme wet environment that they are located. Yet few manufacturers opt for materials that are resistant to corrosion for example stainless steel, due to the greater public demand for colour, shape and general aesthetics.