I also like the Trustfires (18650). I have a couple of 18650 Ultrafires that are problematic. Some times they don't shut off in the chargers. The red charge light stays lit for several hours and come off the charger quite warm. They measure 4.1v fully charge while my Trustfires fully charged are 4.21v. I tried them on 2 different chargers. A Trustfire TR-001 and an Ultrafire WF-139. I have 4 Ultrafire 18350's that work okay.