Under or over? Nantucket Sinks 27 inch single bowl dualmount granite composite lets you choose what type of installation you want; it can be used as a topmount or undermount. With benefits long known to design professionals, this sink is 80% natural stone which helps it to be both resistant to stains and scratches. Because of its material composition, it can withstand thermal shocks and temperatures up to 560 degrees Fahrenheit. The rear placement of the drain provides you with more under counter space for storage. Stone is naturally sound-absorbing for a quieter kitchen. Classic matte white finish makes for a timeless color! Sink drain sold separately.