The electrostatic potential at the shock causes incident solar wind He2+ and H+ distributions to slow differentially across the boundary. This differential slowing produces a He2+ ring-beam distribution immediately downstream from the shock. The velocity (with respect to the downstream H+ distribution) and angle (with respect to the downstream magnetic field) of the ring-beam distribution are determined from a simple model that uses the change in velocity experienced by the protons across the shock, the shock normal, and the downstream magnetic field direction. This simple model is tested with data from the ISEE 1 and 2 spacecraft. Model and observations are found to agree reasonably well for quasi-perpendicular shocks over a wide range of plasma &bgr; and Mach number. The predicted angle that the ring beam makes with the magnetic field can be significantly different from the observed angle for quasi-parallel shocks. This difference is probably due to the fluctuating magnetic field direction downstream from the shock.¿ 1997 American Geophysical Union