Bought 2 of them from drop.com on 2 different occasions. After some time BOTH of them went glitchy. One would simply ramp to the max as soon as the battery is inserted. While the other would just dim to minimum. All instructions are followed, using flat top 18650 batteries, rescrew/cleaning tail cap. Have to junk them BOTH and go back to the trusty Solarforce L2. Just throw any 18650 in there and it works every time.