Review on 🔊 Adjustable Swivel Tilt Speaker Wall Ceiling Mount Stand - Black Bracket with Retractable Telescopic Arm - Ideal for Home Surround Sound System Bookshelf Satellite Speakers - Pyle PSTNDC31 (Pair) by Steve French

Robust, flexible solution for mounting ceiling speakers. I would suggest providing an installation template online so you can find out what the dimensions are and where the holes are so a person can easily tell if it will fit them. Second, change the mounting holes on the flat board. For example, the middle set of holes measures 4 1/8 inches on center. If you change them to 100mm you can easily mount speakers like the KEF Q50A which have keyhole mounting slots 0.100mm apart. Measurement in home audio/video equipment. I worked with the files a bit and just used them for this. Good reliable devices.