These OptoSigma VRB-046-C0 Special Crossed Roller Bearing Goniometers are unused in their factory packaging. These are a 40mm square top, with M4 drilled and tapped holes on the top. These are specials that utilized a curved crossed roller bearing instead of the brass dovetails normally used. The actuator knob can be used manually, but is a cog-belt drive pulley so this was designed to be motorized and used repetitively. The drive is a worm gear and rack setup, so no springs are used. Travel is +/- 5 degrees.