The B-28 lens was originally designed for the Olympus IS system, but works very well with digital cameras and on camera lenses. I used it on a 24mm vivitar lens. Since the B-28 magnification is 0.8 times, the 24mm becomes a 19mm lens. This works perfectly for astrophotography and is cheaper than fisheye lenses. The B-28 has 55mm threads, but will fit on any lens with stepping rings. Lens is in perfect shape, the front cap has some wear. $70 U.S. dollars, which includes regular shipping to any North American destination. Insurance, if wanted, is extra. International pays extra. Cash or International Money Orders only (I live in Canada).