Small gray card case for camera

We have created a case to easily carry 18% gray cards and white cards used to properly adjust white balance and exposure for SLRs and other sophisticated digital cameras. It is designed to fit the GC-2, a credit card-sized gray card from a manufacturer called JJC, so it fits nicely by fixing it inside with adhesive tape. Of course, you can also use other brands' products, or if you want, you can make your own! Two M3x20mm screws are required for assembly.