Review on Cloudray USA CVD ZnSe Focus Lens: 15mm Diameter, 38.1mm Focal Length for 10.6um CO2 Laser Engraver Cutter (40W-200W) by Michelle Langley

Bought this to replace the standard lens in my K40 laser in addition to Si mirrors, and was impressed with the results. I had never heard of the Cloudray company but decided to take a chance as this lens was slightly cheaper than its counterparts (which also had names I hadn't seen). If this lens is indeed the CVD ZnSe advertised then the price (I paid 20) is pretty good. I've definitely seen a significant improvement in cutting/engraving performance over the standard lens and it's held up well so far.