This is a double-arm heavy duty boom for stereo microscopes. It offers a long and flexible working distance that is capable of covering large-and-wide, horizontal and vertical areas. This stand allows you to turn microscope head around three different axis (x, y, and z), allowing you to point the microscope head in ANY direction you wish. While the solid-steel, table-top, rectangular base provides a solid foundation to fit your observational needs.The diameter of the holding ring is 3" (76mm). This rugged boom stand weighs about 50 lbs. It is an ideal stand for gemologists, collectors, engravers and engineers in industries. This stand is brand new in box.Specifications:3" (76mm) head holder ring30" overall length20" double arm17" high pillar10-1/4" x 8-1/4" x 2" solid cast steel base50lbs shipping weight