This yo-yo gives you double action as it comes with two sets of shells allowing you to easily convert the OffString from a super large off string yo-yo to a string play yo-yo with a twist of it's caps. Why choose when you can have both with this transformable yo-yo. The halves lock securely in place with a clever locking mechanism, just twist the caps to unlock the halves and change the rims. This is the re-mastering of the FlyMaster we have sold in the past.