  Observations of Type II supernovae imply that a large fraction of its
progenitors experience enhanced mass loss years to decades before core
collapse, creating a dense circumstellar medium (CSM). Assuming that the CSM is
produced by a single mass eruption event, we analytically model the density
profile of the resulting CSM. We find that a double power-law profile, where
the inner (outer) power-law index has a characteristic value of -1.5 (-10 to
-12), gives a good fit to the CSM profile obtained using radiation
hydrodynamical simulations. With our profile the CSM is well described by just
two parameters, the transition radius $r_*$ and density at $r=r_*$
(alternatively $r_*$ and the total CSM mass). We encourage future studies to
include this profile, if possible, when modelling emission from
interaction-powered transients.
