When we're fighting for our life in the dark hours of an ultra, we appreciate the ultralight build and intelligent lighting of Petzl's Swift RL 1100 Headlamp. The Reactive Lighting tech auto adjusts to the conditions, giving us the illumination we need, while the Lock function ensures a brow wipe doesn't accidentally alter our settings. Whether we're pushing off our knees on steeps, making up time on flats, or scrambling along ridgelines, the split, ergonomic strap holds the light steady, and the IPX4 rating gives us confidence that the rain showers washing away our sweat won't turn off the lights. Equipped with a five-level gauge, the rechargeable, replaceable battery lets us know quickly at the aid station if we need to swap it out.