Abstract: A hanger for hanging a string of conduit within a wellhead has a metal-to-metal seal. The hanger has a body that locates within the wellhead and provides an annular clearance between the body and the wellhead. A locking device fits within this clearance to lock the hanger against axial movement. The metal-to-metal seal is an annular ring with inner and outer cylindrical sidewalls. The seal has a cavity into which a wedge ring is driven to urge the sidewalls apart to embed within the hanger body and wellhead bore. The locking device has reacting wedges that urge a split ring outward into engagement with the wellhead. A retaining mechanism is then moved downwardly with the seal to retain the split ring in locking engagement.