You can see if you've got the feature yourself - just log into Facebook on the web, open up a group chat window, and you might see a phone call icon and a notification that the new functionality is now available to you.
The same group calling option in April, so now those of us using old-fashioned computers rather than phones can get involved too. There's no word yet on when the feature might make it to everyone's account, but there seems no reason why Facebook would take its time pushing it out.
Extra ad blocking
Of course the advantage Facebook has is that pretty much everyone's already on the network - although people are perhaps less likely to have office colleagues added as friends, and this is a feature with uses for both work and leisure.
At the moment the trial is restricted to parenting products and alcohol-related ads but Facebook says it may expand it further in the future. While the social network has let users tweak ad settings for a while, this is the first time it's offered the option to pro-actively block certain topics that might be upsetting.