For those times when you're trying to tie on a #24 trico or a #18 BWO in low light with trout rising around you. The Firefly is engineered so the 2.5X magnifier and headlamp are aligned to make tying knots much easier. The Firefly clips easily to your hat for handy flip-down access and makes for a great fly fishing gift. The bright 3-bulb LED is water resistant and can be removed for daylight fishing. 2 x 3V 2016 lithium battery. USA.