3D Google Cardboard kit is optimized in 3D printing. He is very ways unencumbered and easy to manufacture and assemble. https://www.youtube.com/watch?t=1&v=uzJ-a_K3tdc We updated the previous Google Cardboard kit. The back panel is changed. Additional parts are added. Don't worry that your phone will drop out. Collect a kit and use with pleasure. Lenses diameter 25mm, focus of 45 mm. Use a little glue.