Just purchased 6 new KeepPower 18350 batteries and they're a slightly different construction than my older generations. The bottoms are now completely flat, lacking the slightly raised platform in the center. The tops are also flatter than earlier versions and are kind of sunk beneath the wrapper. They work fine individually but they no longer work in 2-cell lights because they don't make contact with each other. No raised top + no raised bottom = no contact. Annoying.