b may preferably be rounded or curved inwardly towards the first foot 24 a in order to avoid catching the free end of either the first foot 24 a or the second foot 24 b on the curvic teeth 18 the first foot 24 a and the second foot 24 b may continue their free curved ends past the first seal seat 21 a and the second seal seat 21 b respectively thus the free ends of the first foot 24 a and the second foot 24 b separate or extend away from the seal groove 17 and curl into an inside of the seal 16 while the specific dimensions can be varied the cross section of the seal 16 may typically be about 0 30 to 0 50 inches high and about 0 30 to 0 60 inches wide the length of the legs 23 a and 23 b may preferably be of the same length and can be of different lengths if desired and typically about 0 10 to 0 60 inches an angular separation of the legs 23 a and 23 b can typically be between about 60 to 135 degrees the first foot 24 a and the second foot 24 b may have the same or a different radius such as between about 0 030 to 0 060 inches yet even though the first foot 24 a and the second foot 24 b can be generally described in terms of a radius it can be seen from fig3 a that they may comprise a part of a polygon with straight sides.