American Photonics ZnSe Focus Lens 18mm Dia for C02 Laser 10.6um. Direct Replacement for Any 18mm Lens (50.8mm(2.0"))

Excellent product much better than the cheaper products well worth the few extra dollars

American Photonics’ ZnSe CO2 laser focus lens solves three of the problems you fumble with when changing or cleaning a laser focus lens. It has a metal ring that gives you a place to safely handle the lens. The metal ring also protects the lens when placed in the lens housing from cracking due to over tightening the holder’s lens cap. Finally, the metal ring also provides a place to label what direction the lens should be orientated in the lens holder and the lens’s focus distance. For these advantages and hopefully quality, you pay a bit more.The lens and its metal ring are made in the USA. This is nice and should make getting support easier if it is needed. The diameter of the lens’s metal ring of the model I have is 18mm and the focus is 2 inches. The manufacturer offers a variety of lens diameters and focus distances. This is a meniscus shaped lens, which offers some advantages over a plano-convex shaped lens.This lens can be used on an unmodified K40 laser. The 4mm height of the aluminum ring means that the lens holder cap will not screw on as completely as without it, but it will work.This is a nice lens with some useful advantages due to the way the actual lens is mounted. I typically get a lot of life out of my laser lens, and I expect this one to last for a good while.