The Secret Weapon to Learn Double Unders:

Speed balls are the SECRET WEAPON in learning to jump efficiently.  Having trained Athletes at over 100 boxes worldwide, we have noticed no better way to learn proper form than by using Speed Balls.  Speed Balls are a FANTASTIC way to evaluate your jumping form (wrists!) and a great way to TRAIN proper jumping technique. Each arm / wrist works independently, not allowing the weaker to coast off the ability of the stronger. This great device is amazing at teaching your arms the need for SYMMETRY and SYNCHRONICITY!

Contents:

Two speed balls