Each of the Medical Plan options cover a wide variety of services, as long as the services are medically necessary (please see the definition of "Medically Necessary" under "Defined Terms") and their costs do not exceed reasonable and customary (R&C) charges. (Please see "Defined Terms" for the definitions of "Necessary Services" and "Reasonable and Customary Charges.") Covered services and frequency limits may vary slightly across the health care companies — Aetna and Cigna. The lists on the pages that follow include examples of covered services, but the lists are not exhaustive, and coverage remains subject to any Plan requirements or limitations and clinical policies. For specific information on the Medical Plan's covered services and frequency limits, please contact the appropriate claims administrator (Aetna or Cigna) directly, using the telephone numbers provided under "Where to Submit Claims." The list of covered services may change at any time.