American Standards Evolution Tubs with their patented Ever clean surface contain some of the best features available today, in an affordable, durable tub that will last a lifetime. These tubs incorporate a patented silver-ion additive right into the circulation piping to protect the pipes from mold, mildew, algae and fungus that would cause deterioration or staining of the pipes in similar competitor models. This tub also features comfortable bathing design with form-fitted backrest and molded-in armrests, as well as: