Category: Cemented Biconvex Lens Material: K9 Glass Material Size: Diameter 34mm Focal Length: 86mm Center Thickness: 12.1mm Edge Thickness: 8.4mm Surface Quality: 60 - 40 Positive and Negative Tolerance: ±0.1 Angle Tolerance: ±3 Function of the Lens: Optical experiments, homemade telescopes, projectors, etc.