The WA1111 lamp will flash if run over 8.5 volts. Three 17670 Li-ion cells fresh off the charger will supply about 12.5 volts, not including closed loop sag and resistance losses. Perhaps stansbrew meant he was running the WA1111 off of two C-sized Li-ions. Anyhow, the WA1111 in an M6 host will output about 800 lumens off of two C-sized Li-ion cells for 3300 mAh / 3800 mA = 0.86 h * 60 min/h = 52 min, or so. Say a conservative 45 minutes. Output will drop as voltage decreases. Dogbert: You can always bore your M4 for Moli 18mm cells and run the Philips 5761 w/ FM bi-pin adapter for the highest output setup available in a standard SureFire host. Only 15 minutes, or so of light can be had, but the output is quite impressive. Throws useable light an easy 300 yards downfield. But if you guys really want a sweet handheld, wait for the upcoming Polarion 30W. About the size of a 2D Maglite, but much, much nastier. The way I see it, Polarion is the Busse of handheld illumination tools, McGizmo is Scrap Yard/Swamp Rat, SureFire is Emerson and Fenix is Kershaw <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> .