I bought a cardboard version of the Google Cardboard viewer. The lenses were not well ground, so there were imperfections in viewing images. The other thing was the sharp edge of the cardboard cut into my nose. I happened to see this Hasbro MY3D Viewer on sale and thought I might be able to make it work for my Samsung Galaxy SIII smartphone. *One of my “good moves”.
At first I had to physically hold my phone against the back of the viewer, but the lenses were good and produced a pleasing 3D image. It wasn’t too long before I saw that someone on eBay was selling this viewer with a modification. They had used a crossed pattern of two strips (I thought they might be velcro on the ends.) attached to the viewer. You could detach the strips to slip in your phone and then snuggly reattach the strip to the viewer.
I happened to have some Scotch Multi-Purpose Fasteners that I had bought some time ago for other purposes. The Fastener system had matching velcro strips and the back of the velcro had a strong adhesive. I cut a couple of short strips for the top & bottom of the MY3D viewer and attached them with the adhesive backing. I then put my phone on the back of the viewer and measured out a velcro strip to attach to the top & bottom of the viewer while holding the phone snuggly. It worked perfectly! I didn’t even need to add the horizontal cross-strip. *Sorry, for not showing the phone being held by the velcro strip, but I had to take the pictures with the phone;-)