Radius is measured in standard solar radii and mass in standard solar masses. It is 0.503 Jupiter masses but has a proportionally larger radius of 1.224 Jupiter radii. Titan orbits Saturn at 20 Saturn radii. For more recent data on covalent radii see Covalent radius. It has a mass of 1.02 solar masses and a radius of 1.27 solar radii. Phoebe orbits the planet at a distance ranging from 180 to 250 radii. It is the region of a ball between two concentric spheres of differing radii. Sharp corners, bevels, pierce holes, and shapes with minimal inner radii are all possible. These values correspond to the zero tide radii. Special cutters can also cut grooves, bevels, radii, or indeed any section desired. The ionic radii of the alkali metals are much smaller than their atomic radii. There is a clear proportionality between pore throat radii and hydraulic conductivity. Potassium, rubidium and caesium are also incompatible elements due to their large ionic radii. Tight curve radii and gradients of up to 2.6% complicate rail operations. The ionic radii of zinc and magnesium happen to be nearly identical.