As standard, you can use concrete paving stones measuring 21x10.5x8 cm as ballast. These weigh approximately 4 kg each and fit well in the ballast holders in terms of dimensions. Alternatively, you can also use sidewalk tiles up to 21x21 cm, curbstones measuring 20x100 cm, or gravel. Follow the ballast weights from the calculator closely! For Belgium, it is recommended to select "Wadden Islands" as the location.