Well, almost 6mm. It’s 56/57mm
I wonder if they changed the product:
Here it says 66mm should be ok (same link scroll below)
Right!! It make sense!! Mine is smaller!! 
maybe this: Amazon.com
Sadly, I can’t find it on Amazon Europe. Hope my experience will help L5 European owners to avoid my mistake! 
Hi guys , does this charger work well for the librem 5 battery as i have a spare battery and normal battery life is pretty grim for my mobile usage and being able to charge the spare out of phone would be a bonus
it says output 4.35 volt on the correct width charger link in amazon , is this a problem for charging a spare battery designed for 4.2 volt
yes as far as I’ve used it works.
Is this still the best option for external battery chargers or is there a better one people have found? I have 2 extra batteries. Any tips or tricks, someone mentioned a risk with over charging the battery and shortening the battery life. Does under charging it matter? Thanks!
https://www.amazon.com/Universal-Battery-Charger-chargering-Samsung/dp/B07SWV43H9
I bought it and max opening is smaller than battery so it’s totally useless! I’m sad that Purism chosen this so long battery instead of someone with standard dimensions
https://www.aliexpress.com/item/33059035109.html
Somewhere on the forums someone said this one worked and they showed a photo of it being long enough.
Thank you so much for your post, lib52 but I’m not sure about it because in Amazon was written same dimensions (max opening 66cm) but in reality not 
I was going to bite the bullet and just buy it but alliexpress would not put the order though (I use vpn and masked cards). There was also only one left in stock if it was right.
It says 2 3/8s inch which is 60.53 mm. Would that not work if the battery is 60 mm? Could one just break off that swinging arm on these models and idk tape the battery in place or find some way to secure it with the extender removed? Not ideal, but if everything else is fine about the charger idk.