Ab wheels

Since Ab wheels are all the same, they consist of a wheel in the middle and two handle bars, how should I ask this question?

I'm trying to ask how many kinds/types of ab wheels are there in the store. Like different color ab wheels and ab wheels that have a different design. How should I ask this question?

Because it wouldn't be clear if i say: How many ab wheels do you have?

And since ab wheels are all the same, I can't say: How many types of ab wheels do you have? Or What kinds of ab wheels do you have?

So what would I say to find how many different ab wheels the stores has in stock?

Thanks!