With that spring you can use any type of 18650 batt. Flat top, button top…
It’s not bent over in that picture but it should be in the actual unit, so button top cells should work. My flat top’s are running fine in my XIN with the spring end curled towards the middle (So button cells will work).
Just so you know most of the parallel lights (Like the Skyway King, Apex 5T6, Small Sun, etc) won’t work without small button top cells since they have to contact the board. Shame since all I run is unprotected flat cells :/. If your planning on running lights in that form factor buttons may be preferable (Though You could always stick a magnet or something on the poles).
I don’t think he’s into parallel lights yet, and I doubt he’ll be soon, but I’ll have to ask him…
Will raised top work well in lights like the X2000, where the battery top is in direct contact with the PCB that’s connected to the emitter? I guess they would be perfect for this if the tail spring pushes hard enough so the battery doesn’t lose contact with the PCB, but if they aren’t strong enough maybe button top are better - if they tilt from the tube axis there’s still some metal to touch the PCB as opposed to raised tops which could lose all contact? Or is it just a potential problem with completely flat tops?