My physiotherapist has advised me against my tennis this toy. Have the Powerball the original Basic bought simultaneously with the GyroTwister Classic, so my husband even equal what to play. Am also very glad that I bought both: the Powerball is slightly smaller than the GyroTwister Classic and so much better for me handlebar. For my husband with his big hands against the GyroTwister is perfect, but runs much more restless and unfortunately is also clearly louder than the Powerball. Only the starting cord is slightly more durable than the Powerball when GyroTwister. Still, I would rather buy in person definitely be back the Powerball as the GyroTwister. The fifth star is there for the hand strap that's just very practical when acclimatization!
