Thank you for your inquiry regarding this item from Prime-Line Products. The Country Of Origin is China.
The bracket incorporates a thumbscrew to lock the flagpost in place, such that any pole smaller in diameter than 1-1/8" should be able to be retained in the bracket.
2-1/2" vertical, and 1-3/4" horizontal.
Thank you for your recent inquiry regarding this item from Prime-Line Products. The maximum flagpole diameter that can be used with this item is 1-1/8 inch. For additional questions regarding this item, or any other product manufactured by Prime-Line Products, please call their toll free number at (877) 649-9740, or contact them by email at firstname.lastname@example.org