3D SlimFit Construction. By integrating the electronics into the fabric with a specially shaped housing, the entire light unit is wrapped in an ultra-thin casing that fits as seamlessly as a contact lens. With a front profile of just 10 mm and weighing only 78 g, the HeadLamp 425 sits flush on the forehead without wobbling or slipping. The headlamp moves with you as one unit and you quickly forget it's even there. Red rear light for added visibility. The new integrated light on the back ensures you are seen by other hikers, cyclists, drivers and adventurers. Pass-Thru+ charging, a pro feature, can completely bypass the internal battery and allows the unit to operate in extreme cold (-20 °C).