sometimes it will help balance the bow. mine is a NAP shock blocker 500 and is only 5 inches long. its got a litttttle weight, but mainly is there to stop shock and vvibration. it has rubber on it, and is filled with some type of powder. i havent gotten around to taking it off and seeing the bows performance with out it though.

i hear for the money the Sims S Coil is supposed to be a good one...