The width (front-to-back measurement) of the sink that can be used is determined by this measurement. DROP-IN SINKS: For laminate countertops with a backsplash, you can install a drop-in sink that is up to 20 1/2" deep. For laminate or stone countertops without a backsplash, you can install a sink that is up to 22" deep UNDERMOUNT SINKS: Consult your installer. These measurements are important to ensure that enough space is allocated for fixtures and backsplash material behind the sink.