3F UL Gear Tyvek Sleeping Bag Liner – Waterproof, Breathable Bivy Cover (Type A & B)

Protect your sleeping bag from moisture without adding bulk

The 3F UL Gear Tyvek Sleeping Bag Liner is a featherweight, Tyvek-based cover designed to sit between your sleeping bag and the environment. It’s lightweight enough to carry on longer treks, yet purposeful enough to help manage condensation inside tents or shelters. Crafted from DuPont Tyvek, the liner emphasizes airflow while offering a barrier against dampness that can sneak into your bag during cool, damp nights.

Two practical sizes give you options depending on your preferred setup. Type A measures 180 cm by 80 cm and Type B offers 230 cm by 90 cm, with modest weights of 130 g and 200 g respectively. This combination keeps gear light and flexible for quick packing after a night under the stars.

What makes this liner stand out

• Very light and easy to compress, designed for hikers who value packing efficiency.
• Ventilated yet protective: helps manage humidity around the sleeping bag while avoiding a stuffy feel.
• Keeps the inside of your bag cleaner by creating a dry barrier between your bag and the tent floor.
• Simple foot-closure and full-foot protection help maintain bag positioning without restricting movement.
• Warmth potential combined with breathable Tyvek material, making it a versatile add-on for cooler nights.

Usage guidance and practical scenarios

• Use with a sleeping bag and in combination with a tent or tarp for best results. It is not designed to replace rain gear or a full shelter.
• Choose Type A for compact solo setups or Type B for extra length in larger bags or taller sleepers.
• Note that the liner is not a standalone bag; its main function is to minimize interior moisture transfer and help preserve warmth.

Clean handling and careful packing will help you maximize the liner’s performance across many trips. The Tyvek layer is intentionally simple and rugged, prioritizing practicality over complex features. If you’re hiking in damp or humid environments, this liner offers a lightweight, space-saving option to support a more comfortable night’s rest without making bold claims about guarantees.