Our Lumia 820 has a removable shell that users can replace with Nokia-made shells in different colors, special ruggedized shells with extra shock and dust protection, and shells that add wireless charging capabilities found in the high-end Lumia 920 to the mid-range 820.
Those are fantastic cases, and a great option for the vast majority of Nokia’s Lumia 820 customers. But in addition to that, we are going to release 3D templates, case specs, recommended materials and best practices—everything someone versed in 3D printing needs to print their own custom Lumia 820 case. We refer to these files and documents collectively as a 3D-printing Development Kit, or 3DK for short. (Editor’s note: They can be found here, here and here.)
3D printers such as the MakerBot Replicator and Form 1 are already being targeted at the prosumer. For those with a 3D printer or access to one, Nokia's Lumia 820 may have become more enticing.