Medicare Supplement insurance is offered to Medicare-eligible employees who work 20 or more hours per week at a participating employer with fewer than 20 employees, as well as their Medicare-eligible spouses. This insurance is also available to Medicare-eligible retirees of a Church of the Brethren-affiliated employer, as well as their Medicare-eligible spouses, widows, or widowers. At the time the individual becomes eligible for Medicare, he or she must enroll in Medicare Part A and part B as his or her primary coverage and enroll in this plan within the six-month enrollment period that immediately follows that person's Medicare eligibility date.