****************************** Please read the profile before purchasing. ****************************** This is a Bahtinov mask for attaching to a camera lens with a 55mm filter diameter. It's made in the lens cap style, so it's easy to attach and detach. It makes focusing easier when taking astrophotographs with a camera lens. The slits are made with many openings to increase light gathering. The fourth photo is a reference photo. Focus is confirmed with Deneb. The structure may be changed due to use. This is a handmade product, so it is listed as "no noticeable scratches or stains." Please refrain from purchasing if you are sensitive to imperfections. Camera lenses and other equipment are not included in the sale.