The Celestron 94216 Dovetail bar is for mounting a Celestron 8" telescope optical tube to a CGE mount or to attach accessories to the top of the optical tube. Having an extra dovetail bar means that a telescope can have its tube rings attached to its own dovetail bar.
The rectangular dimensions of the dovetail bar are approximately 13.1" x 4" (please see the pdf file below for the item schematic and exact details).
Product carries full 2 year Celestron factory limited warranty (within US/Canada only).
Diagram: Celestron 8" Dovetail Bar Diagram (PDF format)