Mystic UL 15˚

Ultralight down fill Big Agnes System bags designed to excel in all conditions

The Mystic UL 15 is one of our most technically designed Big Agnes System bags, using our Flex Pad Sleeve design, a very durable nylon ripstop shell fabric, and super cozy 850 fill power DownTek™ water repellent insulation. This bag combines ultralight versatility with a long line of packable creature comforts. Whether you’re a 3/4 length-pad-carrying, fast fly tent-gram-counter or just gearing up for a trip where weight and packed size is important, this is the go-to bag for you.
$319.96 to $343.96 $379.95
100% Guarantee


Our top priority is to provide customer service as stellar as the award-winning products we create. If one of our products does not perform to your satisfaction, contact our customer service team and we will help you find gear that fits your needs.

Specs + Sizing

Bag WeightRegular: 2lb / 907g / Long: 2lb 5oz / 1.05kg
Fill WeightRegular: 14oz / 397g / Long: 16oz / 454g
Compressed Bag SizeRegular: 6" X 7" / 15 X 18cm / Long: 7" X 8" / 18 X 20cm
Stuff Sack SizeRegular: M 8" x 17.5" / M 20 x 45cm / Long: M 8" x 17.5" / M 20 x 45 cm
Sleeping Bag TypeBig Agnes System Bags


The lightest Big Agnes System bags offer technical, roomy sleeping spaces for those who aren't willing to sacrifice comfort or compressibility 

Streamlined silhouette for increased thermal efficiency 

Flex Pad Sleeve features stretch construction that accommodates multiple pad widths, and easily connects your bag to your pad  

Regular and Long bags fit 20" - 25" wide pads

Free Range Hood gives you the freedom to lift your head. Jacket-style hood opening contours to the shape of your face for a comfortable, snug fit

Rectangular shaped bag

DownTek™ - a water repellent down that uses a PFC-Free, bluesign™ approved chemistry

Anti-snag zipper for a smooth, quick zip 

Regular: 65" / 165cm YKK #5 anti-snag locking zipper

Long: 70" / 178cm YKK #5 anti-snag locking zipper

Zipper Garage 

Mate together left and right zip bags

No-draft collar, no-draft wedge, no-draft zipper

Interior fabric loops for sleeping bag liners

Exterior loops for hang drying or storage

Mesh storage sack & polyester ripstop stuff sack

Construction + Materials

Nylon ripstop shell fabric with a water repellent finish 

Nylon taffeta lining 

Insotect Flow™ construction

850 fill DownTek™ - a water repellent down that uses a PFC-Free, bluesign™ approved chemistry.

Here’s what other people think.

What’s in a Name?

In 1901, the town site of Mystic was named by Fred May, a settler and rancher, after his boyhood home in Mystic, Iowa. Mystic was located at the head of Trull Creek, beyond the head of the Sleeping Giant. The Elk Mountain School operated there from 1911 to 1942. Now the land is literally nothing but a cross roads to the west of Steamboat Springs. It’s home to a cattle ranch, the occasional tumbleweed, and the whispers of the pioneers who once lived there.