Kraus KGU-413B 31 inch Undermount Single Bowl Black Onyx Granite Kitchen Sink – Single Bowl Sinks – Amazon.com Product Description. Kraus undermount stainless steel sinks are designed with your kitchen in mind. Constructed from premium 16 or 18 gauge T-304 stainless steel for maximum durability, the extra-deep basins accommodate large dishes with ease. At one time, drop-in sinks were the only game in town. Even after undermount sinks hit the residential consumer market, they remained exotic and premium for a number of years–more difficult to install and more costly to purchase. HomeAdvisor’s sink installation cost guide offers average prices reported by customers who have had a kitchen or bathroom sink installed or replaced. See styles, materials and more. Enter your zip code for local costs. 1. Distinctive Features: The edge lip of the sink is mounted below a solid surface countertop, so the sink effectively hangs underneath the counter, as opposed to sitting on top of it; creates a continuous flow from countertop into sink. 2. Countertop Compatibility: Best suited for solid surface countertop materials like granite, soapstone, marble, or concrete. .