If we owned only one headlamp, the 200-lumen Apex would be it. It’s bright enough for mountain biking and backcountry skiing, it’s waterproof down to three feet, and an extension cord allows you to wear the rechargeable battery pack on your belt (or stash it in your pack). An included Velcro strap makes mounting the Apex directly to your helmet a cinch.
A lumen is a unit of measure that expresses total light output. The higher the number of lumens, the brighter a headlamp or flashlight is. Along with beam distance (how far the light travels) and battery life, it's one of the primary factors to consider when comparison shopping.