3F UL GEAR Tyvek Sleeping Bag Cover Liner Waterproof Bivy Bag Camping Bags Ventilate Moisture-Proof Warming Every Dirty Inner Liner BIVY Sack (Type B)Type A, Size: 180 cm x 80 cm, Material: DuPont TYVEK, Available Size: 16 cm x 8. 5 cm, Weight: 130 g Type B, Size: 230 cm x 90 cm, Material: DuPont Tyvek, Available Size: 16 x 8. 5 cm, Weight: 200 g Product features: super light, prevents condensation, comfortable, ventilated, any dirt, heat preservation Notice: Use with a sleeping bag, not alone! We recommend using with curtains or tarpaulins! Its main function is to prevent condensation inside the