Eyepiece Orion Sirius Plossl 25mm Orion Telescopes & Binoculars · Sirius Plossl 25mm Key specifications Focal length25 mm Apparent FOV52 ° Barrel size1.25" All specifications Elements4 About 25mm 52-degree Plossl eyepiece; Orion's standard 4-element Plossl line.