-There's more than one reason why cushion-cut diamond engagement rings are so popular. The unique shape and rounded corners of cushion-cut stones increase the facet size, meaning they give off an elegant and sophisticated sparkle. The cushion-cut diamond is one of the most classic and recognizable diamond shapes to date. This glimmering engagement ring features a cushion-cut center stone set in a diamond halo. It is raly one of the most popular engagement ring.