I can run this light for several hours off 3 C's (PVC adaptor 1” sched. 40) and get outstanding output or I can put 3 AA’s (PVC adaptor ½ sched. 40) or I can turn the spring around and put 2 D's in and still get decent light. It's built using a hotlips and is very well thermally protected (lapped surfaces for the emitter-sink connection, very thin layer of artic silver epoxy, and artic silver III in-between the Hotlips and Mag body) when drawing 1 amp from 3 C's (man I cant wait to get some NhMh C cells…), with 2 D’s it draws very little power (40mA) but I’m not sure how long the V will hold out to even power it, Runtime tests are in progress. I used a sputtered Mag reflector to get rid of what slight yellow tinge it had and to round out the beam and then use a UCL lens to get every Photon out of it as possible. Last but Not least the "SKYWLKR" Logo on the tail cap. Beam Shot's with each battery combo to follow soon.