76mm Diameter Microscope Stand Holder Bracket Stereo Zoom Microscope Adjustable Industrial Trinocular Binocular Microscope Arms76mm Diameter Zoom Stere Microscopes Adjustable Focusing Bracket Focusing Holder For Tinocular Microscope Binocular MicroscopeSPECIFICATIONS:Brand new focus rack with ball bearingFocus gear with coarse focus and tension adjustmentDiameter of annular ring holding microscope head: 3" (76mm)Diameter of opening for stand post (arbor): 1.26" (32mm,25)