Angled Speaker Wall Mount

This is a speaker wall mount I designed to hang my rear surround speakers up near the ceiling. My speakers are Monoprice brand and the back faces measure 100mm wide by 160mm tall. Depth wasn't pertinent so I don't remember it. The angle of the bracket was just right so that the bottom the speaker came 5mm from the wall. The center hole is sized for the machine screw that fit my speakers: 1/4" diameter. I think this is a standard size for speakers but I'm not sure.

Including the design I