[6675]77EDII Rack & Pinion Focuser Set Part # 6675 Description 77EDII Rack & Pinion Focuser Set Aperture 77mm ED Focal length 510mm F-ratio 6.6 Lens configuration 2 elements in 2 groups Coating Fully multi-coated Physical length 420mm Tube diameter 80mm Weight 1.6kg Filter 77mm & 82mm (lens cell) Parts included 2179, 7803, 7051, 7801, 9850 & 7504 Notes BORG rack & pinion focuser version. 2-inch opening & M57-thread.