Backpacks are like best friends that hug you and keep you safe. They've always got your back and, as long as you remember to bring them along, will be there for you no matter what. But when you're out breaking trail and your backpack is left to bring up the rear, who has your backpack's back? The ARVA Helmet Holder is one candidate. It keeps the lines of your backpack* tight for the descent, but gives you a tidy location to store your helmet for the climb.
* Note the holder is designed for ARVA packs but adjustable enough to work with most backpacks that have lateral compression straps.