the tie back sleeve 14 has a polished bore which cooperates with an outer seal assembly 16 on a casing string 15 the seal assembly 16 is slidably and sealingly received in the tie back sleeve 14 where the bore of the casing string 15 is larger than the bore of the pbr 13 the pbr 13 has an a upwardly facing landing shoulder 17 and a retrievable landing assembly 18 is adapted to seat on the shoulder 17 and is provided with latching lugs 19 which are received in an annular latching groove 20 in the pbr 13 annular seals are provided above and below the latching lugs 19 to seal off the landing assembly 18 with respect to the bore of the pbr 13 the retrievable landing assembly 18 normally has a tail pipe or tubular member 22 with landing profiles or internal shoulders 23 for receiving plugs or the like the retrievable landing assembly 18 is set in the pbr 13 by a setting tool not shown which actuates the latching lugs 19 into locking engagement with the locking groove in the pbr after the retrievable landing assembly 18 is positioned in place a tubing string 25 with a sealing assembly 26 can be provided where the sealing assembly 26 is slidably and sealingly received in a polished bore of the pbr 13 and the tubing string 25 is in communication with earth 39 s surface thus the retrievable landing assembly permits the bore of the tail pipe 22 to receive sealing plugs so that the tubing string 25 can be pulled or replaced while not affecting the well bore below.