[Model]: Metal Star Terran 4mm, 10mm, 20mm Eyepiece for Astronomical Telescope [Focal Length]: 4mm (high-power eyepiece), 10mm (medium-power eyepiece), 20mm (high-power eyepiece) Size: Standard 1.25-inch / 31.7mm general-purpose accessories for telescopes [Coating]: Optical lens with full coating, high definition