Mountain Equipment Xenith I Down Sleeping Bag

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UOG TOP PICK – For Fast-and-Light Summer Nights: Weighing just 385g with 900-fill down, strategic baffle mapping, and a minimalist hoodless design, the Mountain Equipment Xenith I offers premium warmth and packability for ultralight missions where comfort still counts.

Mountain Equipment says: 

A superlight bag that will work when other minimalist bags have given up. Premium materials coupled with class leading down control and our Alpine Fit keep you warm
night after night

Our Verdict

Mountain Equipment’s Xenith I is an impressively lightweight down bag that doesn’t compromise on detail. At 385g (Regular), it’s squarely aimed at fast-moving mountain days and nights where every gram counts. The hoodless design helps trim bulk and pairs well with an insulated jacket in milder conditions. The Alpine fit is close but not restrictive, with a generous offset foot-box that avoids pressure points.

With 148g of high-loft 900-fill down, the Xenith I delivers warmth with impressive efficiency. The premium fill traps heat quickly and holds it well, aided by a baffle layout that maximises loft where it’s most needed. Vertical baffles across the chest prevent sag and cold bridging, while angled baffles through the legs keep insulation evenly distributed through the night. It’s rated for a solid night’s sleep at 5°C, making it a strong choice for summer trips. 

The new Plasma 10D fabric is light, supple and breathable. Moisture management is impressive for such a lightweight material, and the fluorocarbon-free DWR effectively repels condensation. The full-length zip makes venting simple when temperatures rise.

– Reviewed by Ultralight Outdoor Gear

Features

• Alpine fit maximises thermal efficiency
• Vertical box wall chest baffles & slant main body baffles
• Stitch-through baffle back
• Ground level side seams
• Grown on anatomically shaped and offset foot-box
• Full length Gemini zip baffle with 110cm zip and integrated neck collar
• Supplied with roll-top stuff-sack and storage cube

Specifications

• Regular weighs: 385g
• Long weighs: 423g
• Fill Weight: 148g
• Std Pack Size: 17cm x 15cm x 13cm

Temperature Ratings

*Mountain Equipment use their own ‘Good Nights Sleep Guaranteed’ rating which they believe is a more accurate number for some sleeping bags and is based not just on the EN test results but on lab testing, their own use, thermal imaging and cold chamber work, along with a lot of data analysis.

• Good Nights Sleep Guaranteed: 5°C/41°F
• Comfor: N/A
• Comfort Limit: N/A
• Extreme:N/A

* As the bag is hoodless, it can not be classified by the EN13537 Standard classification, hence the N/A rating. 

Material & Construction

• PLASMA 10D fabrics throughout are incredibly light and breathable with fluorocarbon-free DWR
• 148g of 90-10 European Goose Down with a minimum fill power of 900

Help & advice:

• Mountain Equipment Extreme Light Sleeping Bag Range
• The Ultimate Guide to Lightweight Sleeping Bags
• Time-Saver Guide to Choosing a Sleeping Bag
• The EN13537 Standard
• Mountain Equipment Sleeping Bag Guide
• All About Down
• Why is ‘PFC Free’ Important?
• Recycled Content in Outdoor Gear