18 5/8" wing arm extension adds additional stability for longer sign installations. Sign Slot: 1.75" D x .3125" W. Hardware to attach arm to bracket to sign included:
" 1 - 5/16" standard set screw
" 2 - 1/4" x 1/2" phillips head flat machine screws
I bought this extension, along with the #800 Metro Wing bracket to mount a 12"x36" sign. I did not use this extension, as it extended past the edge of the sign a few inches. The sign seemed to be supported adequately by the #800 alone, so I just went with that. This extension would be good for signs longer than 36" when used with the #800. Other than that, it is well made, shipping is fast, and ordering was easy. Very happy with Hall Signs.