A drop in bathtub is a tub that is “dropped in” to a frame or structure known as a surround. These tubs feature a rim around the top to fasten to the top of the frame, which can be tiled or built out of wood or other materials. The outside of the tub is concealed by the surround, leaving only the rim visible.

A drop in bathtub is installed by being lowered into a prepared support structure. The tub’s upper edge is rimmed with an outward-extending lip that rests on the top of the support structure. If the bathtub’s bottom is going to rest directly on the bathroom floor, it is usually set into a frame or platform of a nearly equal height.