G2 lens is the best choice for short ranges, as in an engraving machine. The G2 lens is a single lens enabling the maximum true power of the laser diode for rapid close-range burning and engraving. Advantage of G2 lens is 95% efficiency, reduces the beam aperture . Downsides Increase the beam divergence (thickness) and the beam profile. Specifications: Product Name: G2 lens Lens Material : Single element ; Coated optical glass Lens Holder : 9mm x 0.5mm thread , 10mm length , brass EFL ( Effective Focal Length): 4.02mm CA (Clear Aperture) : 5.1mm NA (Numerial Aperture) : 0.6mm Coating : 400-700nm Realpoo Optics can offer laser collimating lens in various focal length, and the threaded casing can be customized. Realpoo Optics is a professional manufacturer of optical glass lenses, such as Spherical Lens, Glass Rod, Fresnel Lens, Diffraction Grating etc. The optics can be offered with coating or w…