This affordable telescope eyepiece offers versatile viewing options for skywatchers of all levels. The focal length varies from 7.2mm to 21.mm with markings of 7.2mm, 10mm, 13.5mm, and 21.5mm. The Orion Zooom! 7.2mm-21.5mm Telescope Eyepiece's design consists of 7 lens elements in 4 groups and includes fully multi-coated optics for clear, crisp images, a 40-degree field of view at 21.5mm, 60-degree field of view at 7.2mm and a comfortable 15mm eye relief, barrel threaded for Orion 1.25" filters.