UPDATE April 19, 2012: To clarify, all three of my review samples were received in October-November of 2011. The first version (batch code V1.10) experienced flickering issues on Turbo. The second (batch code V1.11) experienced an emitter failure. The third was also batch code V1.11, but apparently with improved emitter soldering. Subsequent to the completion of this review, I understood Nitecore was going to adjust to lower return set point for the thermal sensor, to try and reduce the variability in the hysterisis function noted in my review samples (i.e., the oscillations between Hi and Turbo). I presume this change was made to later V1.11 lights, but have no specific knowledge. Recently, a V1.12 has appeared on the market, which seems to have a circuit change causing the red LED ring around the on-switch to light up continuously when the light is on. But there may have been other circuit changes introduced over time, including throughout the V1.11 batch run.