The Kalimar 500mm f/8 MC Mirror Lens is a telephoto lens designed for Canon cameras with a Pentax K mount. Made of aluminum, this lens has a focal length of 500mm and a maximum aperture of f/8. It features manual focus and comes with a case for easy storage and transportation. The Kalimar 500mm lens is a high-quality unit that is compatible with filters less than 20mm in size, making it a versatile and reliable option for photography enthusiasts.