unthreading from the stub 50 in the alternative the anti rotation device 24 may slip over the stub 50 and be pinned in place to captivate the cup 48 similarly the cup 48 may be attached to the stub 50 or to the anti rotation device 24 in any suitable manner as by extending a fastener not shown through a passage 60 in the cup 48 the resilient cup 48 may typically be made of rubber or similar elastomeric material and is sufficiently flexible so a lip 62 stays more or less in contact with the interior of the casing string 40 when the tool 10 is horizontal and the lip 60 is distorted by the weight of the tool 10 resting on its side it will be seen that the lip 62 is formed from converging sides 64 66 so that pressure from above spreads the lip 62 into a more secure engagement with the interior of the casing string 40 many conventional swab cups include a metal reinforcing rim 68 and such features do not detract from operation of the cup 48 for present purposes the cup 48 may be concave toward the upper end of the tool 10 so that pressure applied from above may spread or enlarge the diameter of the cup 48 from a size approximating the diameter of the tool 10 in its running in configuration to a size larger than the set diameter of the slips 14 16 there is an advantage of the cup 48 being on or near the bottom of the tool 10 rather than on the top if the cup 48 were above the slips 14 16 and the tool.