Thorlabs' N-BK7 Best Form lenses are designed to minimize spherical aberration while still using spherical surfaces to form the lens. They provide the best possible performance from a spherical lens for collimating and focusing beams. We offer best form lenses uncoated, or with an AR coating for 350 - 700 nm, 650 - 1050 nm, or 1050 - 1700 nm.