Eyepiece Orion Sirius Plossl 12.5mm Orion Telescopes & Binoculars · Sirius Plossl 12.5mm Key specifications Focal length12.5 mm Apparent FOV52 ° Barrel size1.25" All specifications Elements4 About 12.5mm 52-degree Plossl eyepiece; Orion's standard 4-element Plossl line.