Under or over? Nantucket Sinks's large single bowl dual mount granite composite lets you choose what type of installation you want. This large single-bowl sink can be used as a top mount or under-mount and accommodates all your kitchen needs. With benefits long known to design professionals, this sink is 80% natural stone which helps it to be resistant to stains and scratches. The nonporous surface is hygienic and helps to ward off microbes. 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. Please tighten the drain by hand during installation to avoid cracking the sink. Please tighten the drain by hand during installation to avoid cracking the sink.