Diameter : D20mm*T4.5mm*F150mm Shape : Plano-convex (PCX) Wavelength : 1064 nm (fiber laser) Material : Fused silica (quartz, JGS1 grade) Coating : AR / AR @ 1064 nm, double-sided Mounting ring : P2 marking Application : Handheld laser welding (focusing) Fitment family : Chutian / Chaoqiang Weiye D20 series; also Qilin, WSX, Hanwei, SUP heads that take D20x4.5 lenses