The 6217 Secondary Focusing Lens Assembly for Light Sources is used to focus the collimated beam from a condenser and create an image of the arc or filament one focal length (3 inches) away. It consists of a 2 inch (50.8 mm) diameter fused silica plano convex lens and a 2 Inch Series flanged lens holder. It has a 1.8 in. (46 mm) clear aperture, and F/1.7. The model 6222 2 inch lens holder is also available separately if you need to mount a different focal length lens.