Watch out, they are modern day caltrops. My son really enjoyed them and I bought him obscene amounts, after he learned to stop leaving them on the floor.

Initially, after stepping on one in the middle of the night, any that I found left on the floor went right into the trash. I assume he dug them back out, being a kid and all. However, he learned.

Eventually, he amassed a giant collection. With his permission, I gave them away to a kid that lives nearby. There were six large tote boxes and several dozen box sets. That kid now wants to be an engineer, though my son went into biology.

So, they are really great and it's even better that the old blocks still work with the new blocks. Just look out, they're caltrops, on par with a four-sided die.