The "D in O" is a milestone development in pan tilt heads. Exceptionally smooth horizontal and vertical pannings can both be immediatlely fixed with one slight turn. Fantastic for telescopes and monoculars as well as video cameras, SLRs and view cameras.
Combined with tripod collar lenses, the "D in O" provides nearly limitless adjustment options, becoming a full 3D head. Both horizontal and vertical camera settings are possible in the 90° position.