Buyer beware! These 10440's on Amazon are indeed 10440's, but are not flat tops as indicated by the picture. Idk if I'm the last one to learn this but I figured I'd
Lithium-ion battery - Wikipedia
Amazon.com: Lankoo USB D Lithium ion Rechargeable Battery, High Capacity 1.5V 12000mWh Rechargeable D Battery, 4 H Fast Charge, 1200 Cycle with Type C Port Cable, Constant Output,2-Pack : Health & Household