 They are commonly referred to by the outer diameter of the outer conductor in fractional inches.Sizes covered under these two standards range from 3/8 to 6 1/8 inch outside diameter (OD) for 50 Ω and 3/8 to 3 1/8 inch OD for 75 Ω.Peak pulse power handling, driven by voltage breakdown, is more or less frequency independent for any given size (and can be deduced by assuming ~300 V RMS per mm of inner to outer spacing), but the average power, limited by losses heating the centre conductors, increases approximately with the square root of the operating frequency.