De-icers push warm bottom water to the surface creating an ice-free area of protection around your boat, dock, pier, or other in-water property. They help protect fish and aquatic species, by allowing for open areas where oxygen can enter the water. Kasco de-icers come with (2) 20 ft. suspension ropes. Use de-icers year-round for improved health and beauty of your water.Open Water Diameter varies depending on temperature and orientation (Angled or Vertical). See Kascomarine.com for additional sizing information.