If you have a Medicare Advantage plan you can have many restrictions on being in "network" or not with coverage varying from one plan to the other. A Medicare Supplement will cover in the US. For foreign coverage you have to go pan C-F. They will have a limit on out of country coverage but will cover you. Plan F will have the best coverage and the highest premiums. Many companies price theirs by your home area. We live on the W. side of Mich. and the same plans I sell here are almost double in Metro Detroit. This is true in most companies. All plans with the same letter are identical but the premiums can vary widely.