The two holes on the back of the Arc are M4 and 20mm deep.

The flanged thumb screws provided in the wall mount kit have 6mm of thread and a further 6mm unthreaded shaft.

Thank you.  Elsewhere I had seen reports that they are M5 like the Beam and Playbar screws.

Hmmm…. you have me questioning and checking….

It is the same size as on the underside of the Beam. I have just physically inserted the screw to check.

My bolt guide only goes down to M6, From my unlabelled collection of M nuts and bolts I have a bolt which is smaller, I assumed to be M5 and then this is smaller still. I assumed M4. The OD of the threaded portion measures up at 4.28mm dia.

Sorry for the confusion. I confirm its the same as the underside of the Beam.

BTW I checked and there are no threaded bolt holes on the Playbar, it mounts to the original wall bracket using a slot and pin system.

OK, so which is it? M4 or M5?

I bought M4 and they were too small

The best answer is the wrong one. The screw sizes are M5. I’ve literally just screwed these in.

whats the spacing between screws like?  I have playbar mount on concrete wall and I’d like to get arc as long as I can use the existing screw holes and screws with arc mount.

I don’t want to drill into the thick concrete wall again it took 3 drills. 

I don’t have the play bar anymore so can’t compare, however, spacing is *approx* 62cm. I was able to recycle the mount I had for the play bar (but that’s a TV-mounted bracket). 

Can anyone verify the distance between fixing centres of the 2 mounting screw on the back of the arc please?

I spoke with Sonos rep this am - They told me ARC will mount on existing Playbar mount with no issues.  only thing you won’t get is the automatic trueplay since the old mount is not magnetic. 

you can still do it manual though. so it works! 

Hi, I have my playbar on the wall with screws into concrete wall. I did not use the wall mount for the playbar. Can I use the same screws in the wall to put up the arc or will I need to drill new holes? 

Thanks