The PC slat has three layers , the top is extra UV layer 0.1mm thickness to offer extra UV protection; middle layer is colored transparent (blue, green, silver, etc.) so the sunshine can penetrate the middle layer; and the bottom layer is black to absorb the sunshine energy to heat the pool water. It’s an anti-algae design because it has a slot hole on the back of the hinge ,so the water can flow between each hinge so no algae can grow inside the hinge
