Share your experience!
I am just trying to insert the 2nd nano sim. However, it doesn't fit in the sledge. While the first sim fits exactly, the second slot is slightly too narrow. Both sim cards have exactly tbe same size.
Have I overseen something?
Hi @Buggybear, welcome to our forum!
That sounds very strange, it should fit just like the first SIM card.
Do note that there is a Single SIM version of the Xperia XZ2 as well called H8216 and the Dual SIM version that is called H8266 (in most markets), so it might be that you have the Single SIM version and that is why the second SIM card does not fit.
If you go to Settings > System > About phone, what does it say just below "Model number"?
Get back to us with this information and you can also take a look at the link that @NunoSEN2 posted to see how to insert the SIM and/or SD cards.
Yeah, thanks. It seems that I had accidentally bought a single SIM version. I didn't even know that these exist.
I am a bit disappointed now and don't know, what I will do next.
Thank you for pointing that out.
Oh, I see. 
That's a bit tricky for me to answer since the return policies can vary a lot between markets/regions.
If you haven't tried contacting the store/seller where you bought the device and explained the situation, I would recommend that you start with doing that, and see if you can for example return the device and choose the Dual SIM version, if that one is available in your market.
You can double check with your Local support team which model of the Xperia XZ2 is available in your market.
Keep us posted!