500mm f/8.0 Preset Telephoto Lens for SLR – This lens is an ultra-telephoto lens which is extremely compact and lightweight for its focal length. This is achieved by using an advanced reflex design. This lens is ideally suited for outdoor photography. It has a fixed aperture of f/8.T-Mount for Nikon DSLR – This T-Mount adapter allows you to mount your T-mount lenses with any of the camera bodies listed. It is also compatible with telescope and microscope attachments.2x Teleconverter – The 2x tele-converter is a T Mount attachment, allowing doubling of focal length with the T-mount lenses. This 2x tele-converter doubles focal length of a lens or a telescope which has the T mount system, so if you have a lens or telescope with focal length of 500mm, the 2x converter will increase it to 1000mm. It can be used on all lenses or telescopes fitted with the T / T2 mount thread.