is is small and lightweight, brightness modes from extremely low to very bright. originally wide reflector covers wide angle of view, which is good for misc work. it is possible to get additionally focused longer-thrower reflector. fed by 16340 powerful lithium accum, also with CR123A lithium battery, which is more powerful and coldproof (however using it as megatorch will deplete battery quickly, but it is long enough to light nearby). possible to put on armband or hang around neck. clip is also included. safety switch by tail twist. waterproof.
cost is about $50-60 with delivery on ebay.
Review of Spark SG3 and Spark SG5 Headlamp and clip EDC lights. (14500/AA/16340/CR123) (http://budgetlightforum.com/node/24281)
it is on my icon.
for backup/occasional use it is better to use this small yet powerful flashlight, itp/olight a3 eos: answer to Survivalism: What are the best flashlights/lanterns/headlamps for under $30? (https://www.quora.com/Survivalism/What-are-the-best-flashlights-lanterns-headlamps-for-under-30/answer/Dmitry-Bryliuk)