The NOS uses a variable resistance that changes its weight during different
phases of the swing. Traditional overspeed devices are 10-20% lighter than                               
your typical driver.  As a result, training with these lighter OS devices many
times make it difficult to translate into speed gains with the driver.  The NOS
is slightly HEAVIER than your driver but it can be swung FASTER.  Therefore,
speed gains are a likely result.

The SpeedChain NOS or Neuromuscular Overspeed Device is the latest in
speed from the makers of the SpeedChain. It’s a swing speed and swing
improvement device that will help you lag, learn to master your swing plane
and improve your kinetic chain. And in most cases we promise that you’ll
increase your clubhead speed by 5-10 mph in just a few swings. The
benefits include longer and straighter drives and increased coordination.
Just a few swings before a round can vastly improve your ability to score