UltraFire WF-501B MC-E (BIN M) 5-Mode 800-Lumen LED Flashlight (1*18650)

Mine only draws 1.4A instead of 2.0 as advertised or the 2.2 to 2.9 others are reporting (the most I ever measured was 1.65A). This means that it isn't as bright as it could be and instead of 600 lumens it is putting out less than 400. I'm not sure why the circuit boards aren't more consistent, but there is no way to know what you will get. Also the light doesn't seem to be well-regulated and the current drops with the battery voltage: 1.45A at 4.16V and down to 0.85A at 3.63V.
There is also a prominent dark doughnut hole in the beam. On mine it isn't a light plus sign, it is a dark hole. I will try to post a picture of it. Even outdoors, you can clearly see the dark spot moving with the beam.
The host is pretty lightweight and needs additional heatsinking if you don't want the LED to overheat. The threads are a little rough and there aren't many, only three rows of threads on the tail, four at the head and throat.