Protonerd: Thanks splinter and bill for the feedback. The form and charging with USB sure makes it interesting, but what you write makes sense, probably they cannot squeeze the same capacity in and still include an USB connector. Everything comes with a price. I was just happy to happen upon this ad due to the conversation we had about USB charging of the battery cell.
No problem! Didnt want you to try it and be disaapointed in the end.
My preferred set up is an 18650 cell in a battery holder wired to a recharge port and kill key. That way you never have to take a apart the saber to charge the battery but you can still replace the battery if you need to. There are many ways to charge it too, a usb single cell lipo charger are really cheap or if you want faster charge times you can buy a charger from one of the saber makers like saberforge or ultrasabers that already have the 2.1mm plug for the recharge port.