High Energy Physics has been consistently pushing the performance of technical superconductors, for the benefit of high field magnet technology. So far the workhorse for particle accelerators has been Nb-Ti, but the practical performance limit has been attained with the LHC. Calls for higher beam luminosity (e.g., HL-LHC), and higher beam energy (e.g., FCC), demand a transition from Nb-Ti to Nb 3 Sn, presently the only practical candidate material offering the required high field performance. This paper provides a summary of desirable properties and performance targets for Nb 3 Sn to satisfy the challenging magnet specifications for upgrades of existing and future HEP accelerators.