  In this paper we develop a new semianalytical approach to quantifying the
density profile of outer dark matter halos, motivated by the remarkable
universality those profiles, for a wide range of dynamical parameters of the
inner halos. We show that our minimalist spherical collapse based model is
robust under significant variations of its input parameters around the
currently known values and we identify the turnaround radius as the most
important scale of the problem. Based on that observation, we argue that the
turnaround radius accurately represents the transition to the external density
profile, and we provide a universal test based on geometrical characteristics
of the outer profile as a proposal for measuring the turnaround radius of
structures.
