Target aperture sights are designed for maximum precision. The rear sight element (often called "diopter") is usually a large disk (up to 1 inch or 2.5 cm in diameter) with a small hole in the middle, and is placed close to the shooter's eye. High end target diopters normally accept accessories like adjustable diopter aperture and optical filter systems to ensure optimal sighting conditions for match shooters. Typical modern target shooting diopters offer windage and elevation corrections in to increments at . Some International Shooting Sport Federation (ISSF) (Olympic) shooting events require this precision level for sighting lines, since the final score of the top competitors last shots series is expressed in tenths of scoring ring points.