We're working out what we think - we'll add our view here!
Big Agnes says:
Whether backpacking or traveling, compressing gear in a water resistant stuff sack is clutch. Our Tech Compression Sacks offer serious compression, easy to configure lid and straps, and a webbing/ladder-lock system that allows for seriously secure scrunch. The smooth exterior makes stuffing in with other gear seamless.
This is a must-have piece for insulation pieces.