The Motic 2108 Ball Bearing Boom Stand is stable with smooth transitions for the maximum amount of working area. The ball bearing mechanisms incorporated into the boom stand provide a smooth transition between multiple areas of interest or samples to investigate. Instead of worrying about the perpendicularity of the extension arm as compared to the sample, the two-pole extension arm system allows you to concentrate on your observation. With 638mm of maximum extension [distance from optical center of microscope to the mounting pole], the stand can accommodate large samples or be positioned away from the work area.