Mountain Equipment Xenith III Down Sleeping Bag

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UOG TOP PICK – For Cold-Weather Performance With Minimal Weight: At 701g with 900-fill down and a comfort limit of -8°C, the Mountain Equipment Xenith III delivers serious three-season warmth in a refined, ultralight build.

Mountain Equipment says: 

Our warmest, lightest bag for when every gram counts. Perfect for ultra-light backpacking and trekking in the high mountains during summer and at lower altitudes in Spring and Autumn.

Our Verdict

The Xenith III refines Mountain Equipment’s high-spec ultralight range, delivering three-season warmth in a package that still feels agile. At 701g (Regular), it offers a significant boost in thermal performance over the Xenith II, pushing comfortably into early spring and late autumn territory with a comfort limit of -8°C.

The 373g of 900-fill down is efficiently mapped with a mix of vertical and horizontal baffles to prevent sag and cold spots, and the bag lofts fast once unstuffed. The Alpine fit is snug but not restrictive, with enough space to move without creating dead air. The five-baffle hood is shaped to sit close and secure, and the integrated neck collar helps seal in warmth on colder nights.

The Plasma 10D fabric feels exceptionally soft and remains breathable in humid conditions. While it’s not the bag for careless handling or rugged bivvies, the build quality is excellent and durable enough with basic care.

The full-length zip and Gemini baffle function well, though the down isn’t hydrophobic, so keeping it dry is key. For remote, cold-weather trips where weight is at a premium, the Xenith III is impressively dialled in.

– Reviewed by Ultralight Outdoor Gear

Features

• PLASMA 10D fabrics throughout are incredibly light and breathable with fluorocarbon-free DWR
• 373g of 90-10 European Goose Down with a minimum fill power of 900
• Alpine fit maximises thermal efficiency
• Vertical box wall chest baffles & slant main body baffles
• Slant baffle back
• Ground level side seams
• 5 baffle low volume anatomically shaped hood
• 4 baffle anatomically shaped and offset foot-box
• Full length Gemini zip baffle with 140cm zip and integrated neck collar
• Supplied with roll-top stuff-sack and storage cube

Specifications

Regular

• Weight: 701g
• Pack Size:19cm x 17cm x 15cm

Long

• Weight: 769g

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: -7°C /19°F
• Comfort: -2°C/28°F
• Comfort Limit: -8°C/18°F
• Extreme:-26°C/-15°F

Material & Construction

• PLASMA 10D fabrics throughout are incredibly light and breathable with fluorocarbon-free DWR
• 373g 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