The "ASAHI PENTAX FILTER 49φ 056 (O2)" is a 49mm diameter orange filter for Asahi Pentax. It is a contrast enhancement filter for black and white film. By passing light through an orange filter, blue, green, and purple colors are rendered darker. By darkening the blue sky, the contrast with white clouds is sharply emphasized. It provides a moderate effect, stronger than a yellow filter but more natural than a red filter. [Condition] No mold or fogging, and no rust on the ring. It is clean. Comes with a case. Thank you for looking.