You can use any lids for this game. Small and light weighted lids are usually the easiest for dogs and the larger and heavier lids are the hardest.
You can even use an upside down turned dinner plates, but these are extremely hard.
When the lids are placed on the carpet, they are easier for the dog to lift and turn. When they are placed on the hard floor, the game becomes harder.
When Miki was younger and we hadn’t played much of these brain games with him, I gave a task to Miki to find a treat under a kettle lid. At that time the task was way too hard for Miki, and Miki hasn’t even tried the kettle lids ever since (though he’d probably master the game nowadays).
So, always remember to start with the easier games and gradually make the games harder.
Here are some pictures of the lids I’ve given for Miki to play with. The single tasks are easy for Miki and he usually gets the treats out in seconds. With larger or heavier lids it usually takes a bit longer.
When I put two treats under a plastic container’s lid, it took Miki about a minute to get the treats out, because Miki couldn’t lift the slippery lid off the carpet.
Once when we played the game with a plastic container’s lid about 15 minutes, the result was this: