Under or over? Nantucket Sinks 27-inch single bowl dual mount granite composite lets you choose what type of installation you want: It can be used as a top mount or undermount. With benefits long known to design professionals, this sink is 80% natural stone which helps it to be 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. The sink drain is sold separately.