Chain link centerstop (Part #CS-CS-M) is shown below sideways.   The peg at the bottom is for sliding on a piece of pipe that will go in the ground.

Dimensions:
Diameter = 6-5/8"
O.D. of Bottom peg (Outside Diameter) = 1-1/2"
Peg Length = 1-5/8"
Material = Malleable Steel