Cushion cut diamond rings are wonderful and look stunning.  Polished Diamonds look great in the cushion shape diamond.  Always insist that the cushion cut diamond is GIA certified.  A diamond that is GIA certified can be trusted that the diamond grading is accurate and correct.  When buying a diamond think about the metal it is going to be set in.  If using white gold consider DEF and GH colour diamonds; if using yellow gold consider GH-IJ colour diamonds.  Also think aboiut clarity and an eye clean diamond starts at an Si1 diamond clarity.  Always insist on Very Good to Excellent cut or make of a diamond as this will giveyou light return and sparkle.  Then look at the carat weight and match this with your budget.  Buying a diamond is simply if it is GIA certified and you are buying from a reputabkle Diamond Company.  The cushion cut diamond looks fabulous and works great for diamond engagement rings.  Do ask questions if we can help with your cushion cut diamond ring.