The way a diamond is framed can have a major impact on how big it looks. For example, a bezel—a thin band of metal that wraps around a gem—gives the illusion of a larger stone. These two rings both hold .25-carat diamonds, but the solitaire on the left seems more substantial than the prong-set one on the right.

Round bexel-set diamond with shared-prong diamond accents in 19kt white gold ($1,350) and round prong-set diamond in 19kt white gold with bead-set diamond accents ($1,300), Scott Kay; 800-487-4898.