Unidentified cactus, 2,5 years old

These cacti have grown so fast I can’t believe it. Normally, if you grow cactus from seeds, you’re going to have to wait several years for them to reach this size. These are only 2,5 years old and are somewhere between 11-13 centimeters tall. My hand for scale.
I’m hoping for some flowers soon, so I can properly identify them.

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