This simple but effective enclosure will fit any 'classic Arduino' shaped development board - we've tested it with the Arduino UNO R3, Adafruit Metro, and Adafruit Metro M4 Express. We rather like this case because it's low-profile enough that you can fit shields on top. There's even a flexi-nub for pressing the reset button!
Best of all, it's LEGO brick compatible! So easy, we think this will enable many creative endeavors.
Comes with two pieces. No dev board included - but we stock em in the shop.