Featuring Low Iron (Low-Iron) glass for enhanced UVA and UVB penetration to your plants for higher quality and yield Our special low iron glass allows for more UV spectrums to get to your plants and flowers. Low iron glass is composed of purified materials free from contaminants that make the glass extra clear. Usually glass has a green tint to it, these are impurities possibly from recycled materials. It has been proven that Low-E glass allows more UV light to pass through.