My son is 7 & really thinks these are interesting. I investigated them at Target and they look like tops with a rip cord and battle area so the tops can 'battle' each other.

BUT several of the packages look like you have to build the top, say you can change out parts, etc.

What is involved with these toys? Too difficult for his age?

Thanks for any info. 

Everything seems really inexpensive and then you run across some thing like this.
What is this for?

Beyblades gadget 

My son loved beyblades. You are exactly right. They are basically tops with a rip cord. The more advanced ones you can change out their tops. You basically battle them. They have a battle stage you can purchase. However, my son chose to make one himself. When he retired his toy box, (now is 13), he kept three of them. They are fun! There is also a cartoon based on them. Similar to a Pokemon cartoon. 

By the way, I think 7 is a good age for them. If you allow it!