The illusion setting is a plate of gold shaped to look like diamond from the top. The setting is usually in prong setting. When a diamond is set on that plate(usually smaller diamond ), it makes it look bigger. That's why it has become so popular in engagement rings. For example I showed one of these engagement rings to a retailer. It had a center diamond of .25(Quarter carat)carat, with white gold plate of a one carat. Even as a professional jeweler, he thought it was a one carat center until he looped the piece. This means that you are paying for engagement ring with quarter of a carat center diamond, while it looks like a one carat center diamond ring. There is also a setting called an illusion setting, and it is being used on bracelets and other jewelry. The shape of the setting makes the diamond look bigger than it is. It will give you an illusion of much bigger diamond.