PRO1D Eta C-PL 37mm Circular PL Polarizing Filter. Purchased about 5 years ago and stored unused. (The cap has been opened to check the condition, but it has not been attached.) The PRO1D Eta C-PL is a PL filter with water-repellent and anti-stain functions. I use other sizes, and it's true that dirt is easily wiped off, making it an easy-to-handle filter on location. According to the manufacturer: A circular polarizing filter that suppresses unwanted light reflections, vividly reproducing the original colors of the subject. It suppresses reflections on water surfaces and glass surfaces, and provides a color contrast effect that deepens the color of the blue sky. It has water-repellent and oil-repellent functions, and achieves ultra-low reflection with a high-precision multi-coating. Durable water-repellent and oil-repellent coating is used. It strongly repels water and oil, and even if dirt adheres, it can be easily wiped off.