Excellent : Highly reflective and proportionately cut.
Very Good : Very reflective with well-cut facets.
Good : Most of the light that passes through is reflected back. The proportions are likely to be less ideal than higher-rated diamonds.
Fair : Light will start to reflect out of the bottom or sides. These diamonds tend to be small so that their lower shine is not as noticeable.
Poor : Noticeably dull to the naked eye. These diamonds are less proportionate, resulting in a less reflective stone.