Review on Cloudray USA CVD ZnSe Focus Lens Dia. 20mm FL 50.8mm for CO2 10.6um Laser Engraver Cutter Engraving Machine 40W-200W - Superior Quality Lens for Precise Laser Engraving & Cutting by Kristen Simpson

Bought this lens to replace the stock lens in my K40 laser in addition to the 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 didn't see). 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. I will say it was a good buy for my situation - the specs say it's good up to a 200 watt laser,