True. Just get a ten pack of Harbor Freight magnets for about $3 and it works fine with unprotected cells that can handle the current (use 3 magnets). Works great with Molicel P42A cells. Those Nitecore usb-c rechargeable cells are expensive. I found it better to get the 80 lumen high cri lantern/powerbank/charger/21700 battery kit for $35 for my spare 15 amp rated protected cell. Gave me a backup light, phone/ light charger, as well as an i series battery that can be used in the E4K or one of the more expensive model lights if I got one later. Sometimes I don't want to have to carry magnets with me.i have a e4k the older one. its pretty nice but to use a reg 21700 u need magnets