A disclaimer may specify mutually agreed and privately arranged terms and conditions as part of a contract; or may specify warnings or expectations to the general public (or some other class of persons) in order to fulfill a duty of care owed to prevent unreasonable risk of harm or injury. Some disclaimers are intended to limit exposure to damages after a harm or injury has already been suffered. Additionally, some kinds of disclaimers may represent a voluntary waiver of a right or obligation that may be owed to the disclaimant. Disclaimers vary in terms of their uniformity. Some may vary depending on the specific context and parties involved, while other types of disclaimers may strictly adhere to a uniform and established set of formalities that are rarely or never modified, except under official authority. Some of these formal disclaimers are required pursuant to industry regulation, qualification for protection under a safe harbor, and other situations where the exact wording of a particular clause or document may be dispositive in the event of a legal dispute. (See e.g., Product liability, Toxicity Class, Rule against perpetuities, Public Health Cigarette Smoking Act.)