A very good clear guide, and my iphone 6s works fine, restored with the new replacement battery. The replacement battery came with a full set of tools, including sucker, screwdrivers, spudgers and even a packet of screws.
I must admit, although the guide was excellent and well illustrated, I found it a bit of a challenge. I don’t know if my age (nearly 80) didn’t help , with a slightly shaky hand! Those tiny, tiny screws that can ping all over the place, and replacing the weenie terminals that could so easily be damaged if you press in the wrong place, I found the worst to cope with. However the guide was very helpful with its warnings, such as when you are getting the old battery out and the danger of damaging the volume button connector if you work too near the top end.
To conclude I think the guide is very good, and thank you.