Jump Soles - Small (Sizes 5-7) Jumpsoles when used regularly and intelligently according to instructions maximize and distribute the workout to your calves and forefoot. Up to 30% of your vertical jump is generated there, and those muscles are available and waiting to contribute crucial inches to your vertical jump. If you're serious about building anything like your vertical jump, having tools is better than having no tools! JUMPSOLES are the only platforms which attach onto your own shoe. The almost 3 lbs of extra weight added to the outermost part of your feet make JUMPSOLES heavier than any platform shoe for a harder workout.