Rotating ball joint seal gives vacuum-tight connection good into the micron range. Ultimate vacuum is determined primarily by the tightness of the vinyl tubing connector which fastens the unground shaft to the ball member. Operate below 500 rpm. Use with unground stirring shafts (8134,9530). Lubricate the 18/11 rotating ball joint with our 8117 Stir-Lube. Bottom joint is 19/22. Upper member is supplied with a vinyl connector.