While mobility is the parameter traditionally measured as a function of time or a differential electric field, the measured mobilities are often converted into a calculated CCS value. CCS varies with size and shape of the ion and is directly related to that particular ion's mobility equivalent diameter. The differential mobility suggest that, under atmospheric conditions, small ionic clusters are only mildly hydrated and do not behave as nanodroplets, underscoring the importance of considering hydration effects when modeling cluster properties.