Spherical lenses are manufactured on a custom basis, or sometimes stock lenses can be modified to suit a given application. Plano-Convex, Bi-Convex or Positive Meniscus (positive focal length) lenses and Plano-Concave, Bi-Concave or Negative Meniscus (negative focal length) lenses are routinely fabricated. Various anti-reflection or other coatings can be applied to the lens surfaces.