This is the PLCX-50.8-149.9-UV, a Plano-Convex Spherical Lens with a diameter of 50.8 mm, sourced from CVI Laser Optics. The lens is designed for use with a wavelength of 266 nm and is uncoated.
The lens's geometry is characterized by its edge thickness of 4.18 mm and center thickness of 6.35 mm. The effective focal length (EFL) is 300 mm, and the radius of curvature (R1) is 149.9 mm. The lens does not have an inner or outer radius.
The lens is made of UVFS material, specifically identified as "UVFS MAL-1965". According to the vendor's information, this lens is in stock and the weblink provided leads to a detailed PDF with more information about this lens and other similar spherical lenses.