I am a manufacturer of artificial pupal chambers for stag beetles and rhinoceros beetles. Based on my experience, I modeled these and created them using a 3D printer. Using a water-absorbing sponge, you can easily create artificial pupal chambers of the same size. Simply dig into the water-absorbing sponge a little with a spoon or similar tool, wet it, and press the mold against it to successfully create an artificial pupal chamber. As shown in the image, there are four different sizes, so please use them according to the size of your stag beetle or rhinoceros beetle. This is a set of all four sizes.