This is a mounting bracket to hang the Ikea Symfonisk bookshelf speaker vertically on an Allspace slotted pegboard or a Container Store Elfa Utility B...oard (I believe - I think the two systems are 100% compatible but I haven't tested). You can also hang the speaker directly on a vertical standard, though it'll be slightly off center and fragile (if you were to hit the speaker and rotate it, the hanger would snap right off and the speaker would fall).
I've included two versions - the one with the wider holes accepts M3 heat-set inserts (I used the cheapies you can get in a kit on Amazon). The one with smaller holes accepts M3 screws directly.
To be honest, there's almost no reason for the inserts, since you'll probably only screw these in once. I just wanted to test them and see how they'd work.
Props to Simmers for their Symfonisk Wallmount, which provided the basic dimensions I needed for this :)