This viewer has two lenses for an easy-to-view method of 35mm slides.

Let's get one thing straight:  this viewer is NOT a 3D stereo viewer, although it has the appearance of one.  It is a very popular viewer because it gives the viewer the impression that he/she is part of the scene.  It is this experience that sets the bi-lens viewer apart from all other slide viewers.

It takes 35mm slides only.  For digital camera buffs, you are out-of-luck!

Many experienced and professional photographers still prefer the 35mm film over the digital - each has their own advantages, but resolution wise, with a good 35mm camera, the latter will outperform any day.  Shooting with 35mm slide film will allow one to take full advantage of this excellent viewer.

The bi-lens viewer was introduced by Sawyers, Inc (the same company who premiered "Viewmaster 3D Stereo" pictures - it was continued to be produced by GAF, who bought Sawyers and licensed the viewer to a couple of other manufacturers to market - there are no differences - the viewer is the same.  It takes two "C" batteries and a GE 245 miniature light bulb, (a GE-14 will work, but not as bright); there is also available, a quartz-halogen bulb which is very bright and runs around $8.00.

An AC adapter is available for this viewer.  You will have longer bulb life if you do NOT use the AC adapter - stick to batteries.  On the expensive halogen bulb, batteries are a must, as it will burn out instantly with an AC adapter - an expensive lesson to learn!

Fortunately, this item appears frequently on E-BAY if you key in the words "bi-lens viewer" in the search column. 

If you are into slide viewing and don't have this viewer yet, you will definately get a different experience looking at your slides through this viewer!