70D UHMWPE Grid: 60g
Tyvek:43g
Perfect to protect the end of your sleep system against condensation and rain if using under a tarp
The UHMWPE version has taped on the inside and is waterproof but not breathable. So it can also be an extra waterproof bag for sleeping bag compression sacks.
The Tyvek version is breathable and blocks condensation in some extent.