Excellent hop up if you are looking to improve your RC! The shaft provides more direct power to the wheels, and you won't have to worry about dropping dogbones. It's provides a nice feel when powering through a drift.
If you plan to buy this you'll also need the 3 racing universal outer diff. It will not fit without it as the shafts are longer than the standard dogbone. Also, this swing shaft is required should you want to upgrade to the 3 racing aluminum hub carriers (both front and rear).