The invention is directed to a novel and useful fluid-tight, metal-to-metal, annular seal which can be repeatedly cycled in a high temperature, high pressure environment. More specifically, the invention provides a metal-to-metal, annular, seal on a radially expandable sliding sleeve which moves longitudinally from a reduced ID section of a bore to an enlarged section of the bore. The seal is disengaged at the enlarged bore section resulting in rapid fluid flow and pressure equalization which would destroy many traditional elastomer seals.