The Yeasn HX-400 is a digital pupillometer for binocular and monocular pupillary distance. Measuring range: PD 45 to 82 mm, monocular PD 22.5 to 41 mm, error max. 0.5 mm. Fixation distance adjustable from 30 cm to infinity, LED target with adjustable brightness, automatic switch-off. Power: two AA batteries. Dimensions 221 x 165 x 63 mm, weight approx. 0.64 kg. Serial number 08071795. Pre-owned unit, fully functional.