The card worked fine in New Zealand, which was the country I cared about as well as one of the countries listed at Amazon, but the letter accompanying the card failed to list NZ, so I had to contact support to make sure it would work there. Once the card was in the phone, I had to fiddle with the settings on my iPhone to make it work. How to do this was included in the troubleshooting information in the letter that came with the card, but it was still a little unsettling.

There are several vendors at the Auckland and Christchurch airports that offer 30-day 1GB SIMs for NZ$25-NZ$29, so if you don't need service on the tarmac when you arrive, buying your SIM at the airport may be a simpler option.

Tried on 3 different phones (2 Android & 1 iPhone) in Italy, didn't work on any of them. Kept asking for a PIN to unlock the sim card. The default PIN that I found through some quick googleing didn't work, at all. Useless.

It is very easy to use.

1) Turn off the phone
2) Take out your SIM card from the phone
3) Put this SIM in
4) Turn on the phone

If you need to setup APN, simply

Profile name: Internet (or 3)
APN: three.co.uk
AND, make sure turn on "data roaming".

Others can be left blank. This is data only SIM.

You are going to receive text messages from three.co.uk, however you may NOT send text messages and make a phone call.
I never had any difficulties to use internet in Europe with this SIM. I stayed in Europe for 9 days and have used ~500 MB (mostly for google map to find where to go). Most hotel, train, stations, airport have free WiFi. I think for most people 1 GB is enough for a month.

I activated this SIM before I left USA to make sure it was working. If you going to stay in London, probably you can buy the better one (i.e., 25GB data SIM card) from the convenience store, otherwise I guess this is an excellent option.

Update 2/24/18: Just got back from Israel, and I am happy to report that this product worked great! It also worked during a stopover in Zurich. As I mentioned before, my phone is an unlocked Android, and the data roaming was set to on while in use. I will definitely buy this product again on a family trip to the UK.

Previous Review Entry:

I bought this for our travel in Israel. We have not left the States yet, but I just placed the sim card in my Samsung J2 Galaxy Prime android phone to test as I have read in the F & Q section here that I can test in the US before use. I turned on data roaming as suggested. It works! Hopefully, it will work as well in Israel. I will find out soon enough. I will update my review when I've used this for the purpose that I bought it.

Perfectly work during my trip. I spent 8 days in Paris and Barcelona. It works everywhere i.e. in the metro, inside of famous places. Easy to install just put sim in you "unlocked" phone then turn on your mobile data and roaming.

This is not 4G/LTE but 3G/H+ is fast enough to look at the map, text with someone, and some internet search. Quite nice for short time travel. 1GB is enough for me. (As you know, there is quite many free wifi nowadays)