Underwriters Laboratories (UL) is a well known mark that certifies products are safe to use. UL tests and evaluates new products to determine what conditions they can safely be subjected to; such as maximum voltage, temperature, sunlight exposure and water exposure. UL then certifies the use of its mark on the product. Products with the UL mark will be safe to use as long as the marked limits are not exceeded. Often times customers require a UL mark because it ensures that a product was designed to safely meet the requirements.