pluses: work great in my u2, and i detect absolutely no loss in brightness. Charges fast, and easy. No rattle in my u2 unless i knock on it as if i were knocking on a door. REALLY CHEAP.
minuses: the top is flat, and doesnt protrude from the battery, so if your light doesnt have a spring on the head, the + end probably wont make contact. Gets warm in charger. Sorta wide- wont work in pm6 3w.
overall: great buy... really cheap, and work GREAT in my u2, actually the cheapest protected 18650s around, and high quality. also, i detect no difference in any of the stages at all. I no longer see any reason to use primaries.