Photographical 2x converter with T2 threads on both sides

This 2x converter is placed between the objective and the camera T2 adaptor ring. It doubles the objective's focal length and can be used with any objective that has a male T-2 thread on the camera side.

-- doubles the focal length (aperture: 2 f-stops down)
-- objective side: female T-2 thread
-- camera side: male T-2 thread
-- short and compact design