In another thread, this was mentioned.
4) "Chinese weighted" tails, for better tail stability/performance.
A basic explanation is here :
http://www.rcheliwiki.com/Chinese_weightsA detailed explanation of what this is and how this helps is found here :
http://www.helifreak.com/showthread.php?t=78453This "mod" causes a significant enough improvement in tail performance, that all recent models of small helis from well known brands have all started incorporating this into their tail rotor design. It is said that this mod makes the tails of small helis perform with the kind of tail stability that is usually seen in their bigger cousins.