3F UL GEAR Tyvek Bivy – Ultralight Waterproof Sleeping Bag Cover

Boost the performance of your sleep system with the ultralight Tyvek Bivy from 3F UL GEAR. Designed as a minimalist, protective shell for sleeping bags, this bivy cover is ideal for fastpackers, thru-hikers, and alpine adventurers who aim to stay dry, clean, and warm—without bulk.

⚡ Ultralight & Packable

• Quilt Style (Type A): 180 × 145 cm (70.8″ × 57.1″), weighs ≈ 135 g (4.8 oz), compresses to a palm-sized 16 × 8.5 cm 
• Mummy Style with Hood (Type B): 230 × 90 cm (90.6″ × 35.4″), weighs ≈ 200 g (7.1 oz), same compact storage

💧 Water-Resistant & Breathable Protection

Constructed from DuPont™ Tyvek®, the bivy blocks condensation and splash moisture while maintaining breathability—ideal for use inside shelters to protect your bag from dampness. Not intended for direct rain exposure; best used with a tarp or tent, or as a liner. 

🛡️ Enhanced Sleep System Performance

• Extends the loft of your sleeping bag by preventing moisture buildup from tent condensation
• Helps keep your bag clean and insulated, improving warmth and comfort outdoors 
• Hiker-tested on snowy alpine peaks; strong enough for arduous backcountry use 

🎒 Minimal Footprint

• Packs down to about 16 × 8.5 cm (6.3″ × 3.35″)
• Lightweight at just 135 g (quad quilt) or 200 g (mummy with hood) 
• Includes a small compression sack for tidy storage

🪶 Key Features at a Glance

• Material: DuPont™ Tyvek® (white, breathable and water-resistant)
• Styles: Quilt Type A & Mummy Type B (with hood)
• Helps protect from tent condensation, dirt, and splash
• Ideal for use inside tents, under tarps, or as bag liner
• Easy to clean—wipe with water; do not use detergent 

🎯 Ideal For

• Ultralight backpacking and fastpacking
• Protecting high-loft sleeping bags in damp environments
• Alpine and winter treks needing condensation control
• Users seeking minimalist gear without compromising performance

Overall, the 3F UL GEAR Tyvek Bivy is an efficient, lightweight addition to any backpacker’s sleep kit—boosting bag life, hygiene, and warmth with minimal weight and bulk.