User-powered weight fires like piston. using kinetic energy to cause quick bursts of muscle contraction for short. high-intensity workouts.

A modified dumbbell that oscillates. purportedly increasing the effects of exercise. 

Get lean and sculpted arms & shoulders
Work-out your arms. shoulders and chest in just 6 minutes a day
Much more effective then dumbbells. this is the revolutionary way to shape and tone your arms!

MAKES A GREAT GIFT TOO !    ;)