We've had numerous requests for this particular lens from customers wanting to make a simple educational refractor or for projection projects (or get creative with your ideas for this large diameter long focal length lens). 150mm diameter (just shy of 6") plano convex lens with a focal length of 4000mm (157"). Edge thickness is 3.5mm, center thickness is 4mm. These are unused in mint original condition. We have had these glass lenses (white glass, not plate glass) custom made and can provide any quantity you may need for your project/production run. This price is unheard of for a new lens of this size! Buy a few! We don't know how long this low price will last!