I decided to test the capacity of these batteries side by side with an identical CR1220 name brand Renata battery. The picture shows the resulting graph. The BlueDot battery tested at 44.9 mAh whereas the Renata tested at 40.4 mAh at a 2.0v cutoff and 10200 Ohm load for both cells. That's about 10% greater capacity in these cheap cells vs the quality name brand batteries. That's impressive! Around 40 mAh is a very respectable capacity for these tiny batteries. However I am still a little skeptical about the BlueDot batteries. They may fall behind a little when it comes to self discharge rate so their shelf life may be shorter than the name brand batteries. This is only my own speculation. I have not tested the self discharge rate because the only testing method that I'm aware of is simply storing them for a period of time then testing their capacity as compared to a fresh cell. Maybe ill revisit this in a year. Anyway, these are good batteries at a reasonable price, especially if you purchase the bulk packs.