This pinch clamp is used to assemble component parts of standard joint spherical and O-ring connector arms. The size corresponds to the ball diameter, the first figure in designating the size of a joint. Size 12-A, 18-A, and larger have a screw locking device. Screw lock provided. Size: 18A. Fits O-ring Connection Size: 7-9. Diagram Letter: E. Kimble Chase #: 675000-1821.