A good quality 17MM 6 point socket (Snap-on, MAC, etc.) will be a few thousandths smaller than an 11/16. Some of the Harbor Fright stuff is about as accurate as a sloppy Crescent wrench.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!