this is a 3D printed version of the google cardboard, especially designed for the Nexus 5. It might work for other phone, but no guaranty... It uses lens and magnet sold in Chinese google cardboard kit, which cost only few dollars.
There is only 2 parts, the main frame, named "mask"
and the lens frame.
The lens frame is designed to be flexible enough so it can be bend, to fit perfectly inside the slots printed on the mask sides.