Undermount Corner Tub . Corner shaped undermount tub bathtubs. The rim of your undermount tub will be placed beneath a material such as tile or stone, giving your tub a smooth and seamless finish. This deep soaking tub with jets fascinating small soaker tub images from www.pinterest.com Modern design adds the possibility of undermount installation, keeping the tub appearance as minimal as possible. It was packaged well, delivery was on time , and i installed it myself. Medium sized would be 50×30, to 60×30, with the largest sizes ended at 72 inches long with a width of 30 inches.