IdealPhotonics' N-BK7 spherical single-lens kit, unassembled, is a standard spherical lens group (with selectable positive/negative focal lengths) precision-machined from N-BK7 optical glass. It provides basic optical imaging functions and requires user assembly and adjustment for system integration.High cost-performance ratio, wide spectral transmittance (visible-near-infrared), and multiple focal length/aperture combinations make it suitable for basic optical experiments and rapid system prototyping.