All three packages I bought had an "L" on the label, so I assumed that meant for a large egg. I used large eggs in the four I did, but they were still a little too big, so next time I'm going to use medium eggs. Actually, I had two large eggs from Japan and two large eggs from the U.S. (bought at the commissary on base). The Japanese eggs were fine, the American eggs were too big.
Hard boil the eggs the way you normally would. I put them on the stove and when the water starts to boil I pull them off the heat and let them sit for 11 minutes. After that I put them in a bowl of cold water to help the peeling process. As you can see below it didn't do much good! I need more practice, but at least with the fish the scale design did a decent job of covering up my mistakes.
The directions were on the back of the package and entirely in Japanese. A friend of mine translated it for me. I didn't write it down but tried to remember what she said. The eggs have to go into the egg mold while warm, and then into cold water once in the mold. So I peeled the eggs, put them in warm water, into the mold, into a bowl of ice water, and about 20 minutes later I pulled them out and hoped for the best. It's easy to clean up the edges; I used a paring knife after they came out of the molds.
These could be used for more than just eggs; chocolate or Jell-o are the first two that come to mind. They wouldn't have the design on both sides, but a flat bottom would be nice for laying them on a dish or platter. Maybe add a little alcohol to the Jell-o making them fancier Jell-o shots?!