Camelbak Octane 18X Hydration Pack. Like all of Camelbak's Octane series packs, the Octane 18X is made of ultra light materials perfect for adventure racing, trail running or XC bike riding anything where you need to move fast and minimize weight. Features a vertical zipper that opens to expand your cargo volume or zips up tight for a snug, low profile. Plus you get two additional stretch pockets on the front and two stash pockets on the waist belt and harness to keep your essentials always close at hand. For safety, it comes with added reflectivity front and back and a whistle on the harness.