the bottom shoulder 107 the collar 111 is threaded onto the top housing 39 s sleeve 108 pulling the top housing 101 onto the bottom housing 103 loading the ring bearing 102 therebetween best shown in fig6 a the ring bearing 102 is sectional comprising a top race 112 a bottom race 114 and an intermediate cage ring 113 fitted with a multiplicity of ball bearings 115 in fig4 one can see that when assembled the bottom race 114 is seen to be supported by and rests on the bottom shoulder 107 the cage ring 113 rests on the bottom race 114 and the top race 112 bears against the cage ring 113 in fig5 the top housing 101 seen to provide a general service rotary section 120 supported on the ring bearing 102 rotation about the vertical axis 20 of the bop 51 the rotary section 120 further incorporates means 121 for controllably and periodically gripping the jointed sections 15 while operations are performed gripping means 121 are installed to grip the jointed section 15 and form a bottom surface 122 for transmitting the weight of the gripped jointed sections through the top housing 101 and into the annular bearing 102 thus the jointed sections 15 are prevented from being lost down the well yet are easily rotated on the annular bearing 102 for making up successive threaded joints of tubing 15 the gripping means 121 are typically a slip arrangement or a split clamp after the gripping means 121 are secured about the jointed section 15 it bottom surface 122 is lowered into engagement with the top housing 101 or rotary section 120 and the top housing bears against the top race and transmits the weight of the jointed section 15.