The 77320 Focusing Spacer Tube Lens Kit consists of a spacer tube and a Borosilicate Crown Glass plano convex lens. Use it in conjunction with the 77258 to focus collimated light into a monochromator. The F/# of the lens matches the input cone of the monochromator. The lens is 1.5 inches (38 mm) in diameter to collect all of the output from an Oriel 1.5 Inch Series source and has a 75 mm focal length. We offer glass and fused silica models.