It is a sack for holding wet shoes, so is there a reason why the waterproof rating is 500mm and the breathability is 15000g?
To put wet shoes in a bag, it seems the waterproof rating should be high so water does not leak out, but the breathability figure is set much higher than the waterproof rating, making me wonder about its use.
It is designed to block water from seeping out inside a bag, while quickly releasing the moisture of wet shoes trapped inside the sack.
The waterproof rating is set relatively low at 500mm, and the breathability rating is set very high at 15000g[1]. Generally, a waterproof performance of 500mm is at the level of everyday water resistance where light water droplets or dew do not immediately seep through, whereas breathability of 15000g is a high specification close to that of functional outerwear that vents sweat and water vapor generated by vigorous activity to the outside.
OZN's Zero: UL Shoes Sack is a shoe sack designed to make storing wet shoes convenient[2]. If shoes soaked in sweat and moisture are sealed in a completely waterproof sack, moisture gets trapped inside, causing odors to worsen or the shoes to spoil easily while staying damp. This sack prevents liquid water droplets from leaking onto other gear inside a backpack, while allowing gaseous moisture to pass outside, reducing the chances of shoes remaining trapped in dampness.
The weight is also light at about 18g, making it suitable for packing into a backpack without burden after changing shoes during outdoor activities where gear needs to be minimized[3]. hmmm, it looks at the sack not merely as an airtight container trapping shoes, but as a ventilation channel that gradually empties out moisture.
Whether the fabric surface has a separate water-repellent coating has not yet been confirmed from official materials.