Abstract: A prosthesis for permanent implantation at a selected body location to establish a desired body contour has particular utility and advantages as a mammary implant. It comprises an outer medical grade elastomer closed envelope having a built-in anterior self-sealing valve and an inner like envelope secured to the posterior of the outer envelope and having an anterior injection receiving area with a self-sealing capability secured in a fixed position of registration to the self-sealing valve. A viscous gel is provided intermediate the envelopes for lubrication to minimize or eliminate the incidence of spontaneous rupture.