This accessory is a base and post assembly designed to work with 2" diameter optical assemblies. The PM90 allows a 2" optical assembly to be held vertically or horizontally and rotated through any angle, and is adjustable to any height above the included base plate from 0 to 12". The included 6x12" base plate can be secured to a standard optical table or left free standing. This accessory can be used with Sciencetech's A1 and A4 Solar LightLine solar simulators to allow for horizontal or vertical operation (and at any angle) by holding to output optic at the end of the 4 foot light guide.