American Standard Evolution whirlpools feature jet technology and designs that give consumers a more relaxing, comfortable, and affordable hydrotherapy experience. The jets are designed to require no height adjustment and are flush against the tub. The proprietary horizontal overflow drain design offers the benefit of safely filling the tub with 30% more water to get the deepest soak available. With an EZ-Install Heater added, users can soak in their tub longer, without worrying about cooling water temperatures. The Evolution Corner Tub includes the EZ-Install Heater. Evolution whirlpools are pre-plumbed to accommodate the EZ-Install Heater, and installation requires only two steps. Evolution whirlpool comes in 5', 5 1/2' oval and 6' lengths as well as a corner design.