backup elastomeric seal 45 that seals against a portion of production casing hanger bore 39 retainer ring 41 also has an inner seal 47 that seals to an exterior portion of bridging hanger 33 above threads 43 the body of bridging hanger 33 has a guide portion 49 on its outer diameter that is cylindrical and has an outer diameter less than the outer diameter of retainer ring 41 a seal surface 51 is formed on the outer diameter of the body of bridging hanger 33 above guide portion 49 seal surface 51 is finished to a desired metal to metal surface finish such as 32 rms seal surface 51 has an outer diameter that is slightly greater than the outer diameter of guide portion 49 but less than the outer diameter of retainer ring 41 a transition shoulder 53 is located between seal surface 51 and guide portion 49 a bridging hanger seal ring 55 is carried on the outer diameter of bridging hanger 33 above retainer ring 41 seal ring 55 has a metal seal 57 on its lower end in this embodiment metal seal 57 comprises a welded inlay of a conventional type of material suitable for forming metal to metal seals for example the inlay may be a nickel base alloy metal seal 57 has a cylindrical surface on its inner diameter and a downward facing tapered surface on its outer diameter the tapered surface mates with a tapered seal surface 58 formed in bore 39 of production casing hanger 27 seal surface 58 is prepared for metal to metal sealing having a finish substantially the same as seal surface 51 on bridging hanger 33 in this embodiment tapered seal surface.