Review on Google Cardboard POP! - Affordable 3D Glasses with Head Strap and Cushion for Android and iPhone up to 6 inches by Vincent Burton

I got it for my mother because it's nicer than cardboard and black ones. I immediately noticed that there was no "button" or magnetic slider to change the image - it's just an empty hole! Then I read the instructions and realized that you stick your fingers in and touch the screen - very easy and probably better than those flimsy magnetic sliders found on other cardboard models. You won't break your finger as easily as one of them.