This is a HO-BXL25-12 25mm Dia. N-BK7 Double-Convex Lens, which has an effective focal length (EFL) of 300mm and is uncoated. The lens is sourced from Holmarc Opto-Mechatronics, a reputable vendor in the optical industry.
The lens is a Spherical Lens of the Sub Type Spherical Lens (Convex-Convex), with a base shape of Circular. The diameter of the lens is 25mm, and the thickness at the edge is 2mm. The lens's inner and outer radii are both 0, and the radii of curvature are r1: 312.540483 and r2: -312.540483.
The lens is made of N-BK7 Schott, a popular optical glass known for its excellent optical properties. The lens is designed to work with a wavelength of 587.6nm. It does not have any coating, which means it is in its most basic form, offering bare functionality.
For more information about this lens, you can visit the Holmarc Opto-Mechatronics website at https://www.holmarc.com/bi_convex_lenses.php. The link is valid and the lens is in stock as of the last update.