I have given these batteries specifically a 5/5 star rating. Personally, I think the price was very slightly too much; however, with the CR1616 batteries on ZedLabz you receive two batteries so the price comes to quite a nice total.
I had 6 Pokémon games that I needed to replace the batteries in and so I ordered 5 packs in order to have 10 batteries total (6, plus some backups). They arrived very quickly, and were exactly as stated on the website (2 CR1616s with solder tabs, for GameBoy Advance cartridges, etc). I personally don't know how to solder so I asked my Dad to do it for me and we followed a tutorial: https://youtu.be/UOEhunvcRv0 . All 6 of my games are now working again AND the save data is still intact. The save data should only be erased if you are replacing the battery of Crystal, Gold or Silver but they use a CR2026 I think so it is a different battery anyway. The soldering tabs on the battery do need to be bent slightly so they can contact the correct areas of the circuit board but that's also included in the video tutorial I linked before.
All in all, this purchase was worth the price. You get 2 batteries which allows you to either fix 1 game and have a backup in case you make a mistake, or you can fix 2 games which is very cost-efficient. The delivery was very quick and easy and I'd recommend this website to anyone who wants to fix games such as; Pokémon Ruby, Pokémon Sapphire, Pokémon Emerald, Boktai, etc.