This is a Plano-Concave Spherical Lens, sourced from OptoSigma, designed for use within the wavelength range of 400-700nm. The lens has a base shape of a circle and is constructed from the material n-bk7 schott. The lens has a diameter of 25.4mm and a thickness at the edge of 4.7mm, with a center thickness of 2mm. The effective focal length (EFL) of the lens is -60mm, and the front and back surfaces of the lens are coated with an Opt M coating. The lens has an inner radius of 0mm and an outer radius of 0mm. The lens is in stock and available for purchase at the provided weblink.