Ball bearing focus rack for smooth, precise adjustment - Smooth operation and reliable hold: built-in ball bearing enables quiet, accurate rotation, while the focus gear provides coarse adjustment and adjustable tension to lock in view without drift. - Secure mounting sizing: annular ring holding the microscope head measures 3' (76 mm) in diameter, and the opening for the stand post (arbor) is 11/4' (25 mm). - Professional, durable design: practical construction with a clean, attractive appearance that remains easy to carry and use in daily lab or field work. - Clear compatibility and use: designed to support standard microscope heads within the specified ring diameter and arbor opening, offering dependable mounting and adjustable focus control. 2-3 practical use scenarios - Laboratory bench: mount a microscope head on the ring, use coarse focus to quickly bring specimens into view, then apply the tension control to maintain a steady observation. - Classroom demonstration: a portable, reliable setup that allows students to see crisp focus changes without drift during explanations or experiments. - Field inspection or electronics work: a compact, easy to transport focus rack that provides smooth focusing and secure head positioning while you examine components or small parts.