tamiya makes excellent hop ups and this is no excpetion. the quality is outstanding and is a very good upgrade for your df03. if you bash hard or race this is pretty much a give in. when you land a jump at full throttle and your wheels stop suddenly, that extra energy can cause your diff to slip and strip out making it worthless. the slipper will prevent that allowing the spur to slip instead of your diff. helps to prevent burnouts from too much throttle. i didn't have any trouble installing this upgrade. just remove the 5 screws on the top of the rear gear box and you can easily remove the stock main shaft and install the slipper shaft. i don't recommend greasing your spur and pinion gear as the grease can ruin your slipper pads if they get grease on them. i even made sure i cleaned the spur gear cover well as i had a good amount of grease in it. i might say if you haven't upgraded your motor you don't 100% need this but it's still a good idea.