This can be used for the common umbrella adapters, swivel brackets, and other lighting clamps and adapters.

The diameter fits the standard 5⁄8 inch (nominal) hole found on many of the lighting accessories cited above.

One end has a 3⁄8 inch X 16 thread stud.  The other end has a 1⁄4 inch X 20 threaded hole.

Price: $5.00 + shipping