The Danubia T2 Teleconverter doubles the focal length of lenses. Suitable for Mirror and Pre Set lenses with T2 mounts, it is screwed in between the lens and the body (using a specific T2 mount for the body) and then doubles the focal length of the lens. The light comming into the lens is reduced by a couple of stops as is usual with most 2x converters, but shutter speeds can be altered to cope with the light loss. The unit is very compact, measuring approximately 2.25 x 1.75 (HxW) inches and is made from metal, with glass optics.