3DKEV Flexible is the term that Shape ways uses for in this case SLS Nylon.
Y9ou can find the material description here:
https://www.shapeways.com/materials/strong-and-flexible-plastic?li=nav
So it is not a rubber like flexible, more a clear plastic tupperware food container kind of flexible, if that makes sense.
According to other people who bought the case it fits perfect.
Hope this helps, thanks Kevin.