Hello! � � The sole of the Vicco Bumba III Orthopedic Children's Sandal is lightweight. Thanks to the EVA and phylon materials used in its base, it allows children to move comfortably. The lightness of the product is particularly emphasized in the descriptions, and this feature is highly appreciated in user comments. With its non-slip, orthopedic structure and lightness, it will be a very suitable and comfortable choice for your twin 3-year-old sons. If you need me to help with something else, as KoraySpor, we are always by your side. � � ♂️