Left-hand panel: comparison of the mass profiles of NGC 4261 (circles), MKW4 (triangles) and A 2589 (stars), normalized to have the same mass at 100 kpc. Note that the shapes of the mass profiles are different even over overlapping radial ranges. Right-hand panel: the same, but scaling the radius with respect to the virial radius (Rvir) and renormalizing each profile to have the same mass at 0.001Rvir.