A drop-in sink or Self-rimming sink is a style in which the sink mounts into the countertop cutout. No polished stone edge is necessary in this case because the sink will overlap every side. An under-mount sink on the other hand sits below the cutout allowing the polished stone edges to show. This style is much more common with our clients; however, costs are higher because of the extra work it requires.
A drop-in sink sits on top of the cutout in your granite counter while an under-mount sink sits beneath the cutout. There is generally an extra polishing charge required in preparing a granite countertop for an under-mount sink.