This 3Dscope viewer is a smart viewer for large formats, from 20 cm wide (A4-size) up to the size of a double barn door. Perfect for viewing parallel pictures on your large computer screen, or even 2 screens next to eachother. On the top of this viewer is a knob, to adjust the mirrors, for watching any large sized stereo picture. For protection of the mirrors and for keeping them clean, there are 2 sliding parts, to close the viewer. A great 3D viewer for every large sized parallel stereoview!