If you get one add-on, this is the one to get! With this upgrade, we install two carbon fiber rods that run down the length of the whole ukulele neck, from the first fret to the 19th fret. Carbon stiffening rods are very strong rods that do not bend; they reinforce the neck to make it even more durable than it already is. The stiffening rods will ensure that your neck bow does not change with temperature and humidity changes. If you live in a place that goes through seasons, or if you plan on traveling with your ukulele, then the rods would be beneficial.