70-120mm, f 3.5, zoom lens for M and S size Imager / Projectors. Change your lenses in a couple seconds by simply unscrewing the tightening knob at the lens holder of the projector. The lens slides in without any other tools. The zoom lens can be pulled away or toward the projector for your focusing. Zoom just as you would a camera lens by the rotating ring at the front of the lens.