The Solar Sun Ring is a passive solar swimming pool heating device made from two sheets of heavyweight U.V. resistant vinyl. The upper clear layer holds insulating air and focuses sunlight on the blue colored lower layer. The blue layer absorbs about 50% of the sunlight and converts it to heat. The balance of the sunlight is allowed to pass through for deep water heating.Common Questions:How Do Solar Sun Rings Work? At night the contained air acts as an insulating blanket to retain heat gained