The Groundsheet Poncho is a 3-in-1 piece: worn as a rain poncho while walking, pulled over the pack as a cover when stopped, or laid flat as a groundsheet under a tent at camp — Zpacks models and other tents alike. That multi-role design means carrying one item instead of three separate pieces of gear, the main appeal for hikers trying to cut pack weight.
It's also compatible for use as a tarp, so on trips run with a tarp shelter it can double as ground protection and rain gear at once. Anyone who wants a poncho cut specifically for comfortable walking, a groundsheet sized precisely to their tent, or a cover shaped exactly to their pack will find a purpose-built version of each performs better individually.