Well, I tried them out. They work OK as weeders. I think it will take some use to figure out how to best use them.
As a cultivator the Cobra head weeder is less than satisfying. It's more like a 1" wide hoe that scrapes the ground.
I was hoping that it would be more curved and pointing back towards the user. It comes down more perpendicular to the ground and doesn't dig in.
It did not break up hard clay without a LOT of work. I went to the spading fork.
Overall, I would give it 2 1/2 to 3 stars. It's well made, but doesn't do anything better than other tools I already have.
