This 5.5mm band is in the classic plain shape of a low domed ring that has a comfort fit interior. A comfort fit interior indicates a slightly domed interior shape.
This is a is fabricated from die struck gold and is not a casted band. Therefore it is stronger and more durable than many others and can always be easily adjusted for size without any invasive work. Of special note is the exceptionally comfortable EURO SHAPE collection which has a fully rounded or "bullnose" edge that feels like "no edge at all".