This is the BICC-25.4-51.8-UV, a laser grade concave-concave spherical lens with a diameter of 25.4 mm, sourced from CVI Laser Optics. The lens is designed for use with a wavelength of 587.6 nm and is uncoated.
The lens features a center thickness of 2 mm and an effective focal length (EFL) of -50 mm. The first radius of curvature (R1) is -51.8 mm, while the second radius of curvature (R2) is 51.8 mm. The lens is made from UVFS material with the catalog number MAL-1965.
The lens's geometry is circular, and it does not have any inner or outer radius specifications. The lens is in stock and available for immediate purchase. The detailed specifications of the lens can be found in the provided link: https://www.idexot.com/media/wysiwyg/cms-pages/pdf/2-Spherical_Lenses.pdf