My 6 yo daughter loves this. It's a great way for her to memorize math facts without even knowing she is doing it. I was worried about them being difficult to use because you have to hold the cards in one hand and wrap with the other, but my daughter has had no trouble.

There are ten boards in the set joined by a rivet. Each board covers one math fact, i.e. -1. You wrap the string from the first number to the answer and then around again to the next number. My daughter loves that she can check her answers on the back by looking at the raised lines.

This is a great concept, except for the ages that most kids are when they will be using them, it is hard to hold and do the "wrap". At that age (around 6) when they are learning math facts, they don't have good enough dexteriety to complete the activity correctly.