I designed this for a new pair of Sony MDR-ZX110NC noise-canceling headphones that I bought for a recent trip. My old phones got crushed in my computer bag, and I didn't want the same thing to happen to these. I took inspiration fro many of the features of this thing from UroBen's "Toolbox for miniature tools". I printed the prototype with ABS, at 20% infill. Use pieces of raw 1.75mm material as the hinge pins. I cleaned up the holes with a #52 machinist's drill bit, which leaves them just slightly smaller than the material. The small holes on the inside of each half will accept 3/16" neodymium magnets, to hold the case closed. The hole in the top half is 3/16" deep, and the one in the bottom is 1/2". Make sure you have the magnets oriented the right way, before you press them in. I get my magnets from https://www.kjmagnetics.com