We're working out what we think - we'll add our view here!
Ultimate Direction says:
Its purpose-driven (FKT attempts, overnight pushes across a range) and yet the Signature Series Adventure Vest is meant to be forgotten. Every detail has been scrutinized so you can focus on the exact details of your route and a personal locator beacon pocket works seamlessly on the vest to let your friends, family, and fans track your big adventures. 4-way stretch material moves with you instead of against you and an upfront phone pocket gives you access to photo opps (if you can stand to stop and revel in the views) on the go.