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Ultimate Direction FK Bivy Review

Ultimate Direction FK Bivy Review

The Ultimate Direction FK Bivy is a bug-proof bivy sack designed to be used under a tarp shelter. It has a self-standing hood with two flexible wire-rods to keep the mosquito netting off your face, backed by solid fabric panels that can be rolled down for added wind protection and warmth. But the FK Bivy is very cramped inside and a lot less comfortable than it sounds. It’s also quite fragile and surprisingly easy to damage, even with light use. I’d give this one a pass.

Ultimate Direction doesn’t make this product anymore. Visit our Top 10 List of Ultralight Bug Shelters for our list of recommended alternatives.

Ultimate Direction FK Bivy

Ease of Entry and Exit

Not Ready for Prime Time

The FK Bivy is ultralight, but not terribly comfortable or durable. While it does provide insect and rain-splatter protection, it's difficult to enter and exit and must be handled with care.

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Specs at a Glance

  • Weight: 6.6 oz (8.2 oz, actual tested)
    • Bivy sack – 7.1 oz
    • 2 wire poles – 1.1 oz
  • Size: Regular
  • 7D Nylon Micro-ripstop, light Cire (this means “shiny”), with PU kiss-coat
  • 20D Nylon Ripstop, calendarized, with Silicone outer and PU inner face
    • Base is not seam-taped
    • No stake-out loops
  • Length: 82 in /208.3 cm (72 in, actual tested)
  • Width: 23″ wide at torso, tapering to 16″ at feet

There are two kinds of bivy sacks:

  • Fully waterproof and bug-proof, minimalist shelters like the Outdoor Research Alpine Bivy that can be used in three or four season weather, instead of a tent and footprint.
  • Sleeping bag covers that provide wind, splash-back, and insect protection, but must be used together with a waterproof tarp, and often with a thin plastic sheet for moisture protection from the ground.
The FK Bivy is designed as a sleeping bag cover to be used together with a tarp
The FK Bivy is designed as a sleeping bag cover to be used together with a tarp

The Ultimate Direction FK Bivy falls squarely into the sleeping bag cover category because it’s not sufficiently waterproof to be used alone in rain. Its main function is to provide warmth by blocking convective heat loss from the wind, deflect any rain that might splash back under your tarp, and insect protection. That said, you could also use it as a standalone shelter for wind and bug protection if rain isn’t an issue.

The hood is held up by two wires
The hood is held up by two wires. Note top snap, to hold wire in place.

Entry and Exit

The first question you want to ask about a bivy sack, is how easy is it to get in and out. Because if you’re like most people, you need to get up to pee at night, especially if you’ve been drinking water all day.

The only way to get in and out of the FK Bivy is through the hood, which I cover in more detail below. You need to slide into it feet first and somehow scootch yourself out at night to stand up, which is awkward and annoying. This product would be so much better with a side zipper, to make the process of getting in and out of the bivy easier and intuitive.

Interior Volume/Space

I’ve owned a couple of bivy sacks and the FK Bivy is the tightest and most claustrophobic one I’ve ever used. The biggest issue is the amount of space available in the area below the hood, from your upper torso to your feet. For example, there’s barely enough space for me to lie on my back, on a 2.5 ” Therm-a-Rest NeoAir Xlite sleeping pad in a 40 degree Feathered Friends hoodless sleeping bag. It’s so tight, I can’t pull up or adjust the zipper of my bag to reduce or increase my warmth. There’s simply not enough room to move. However, there is a marked improvement in interior space if I switch to a thinner 1″ thick Therm-a-Rest Prolite sleeping pad, but forget about using this bivy sack with a thick pad and/or a puffy cold weather sleeping bag. It’s just too cramped.

The only way to enter and exit the FK bivy is through the hood
The only way to enter and exit the FK bivy is through the hood

The FK bivy also has a sleeping pad sleeve to hold your pad in place, but it still slides around because the strap is wider (22″) than a 20″ pad and the interior floor of the bivy is very slippery. If you don’t mind the extra weight, it’s best to use the FK bivy with a full length 72″ long mummy sleeping pad, so it can’t slide as far down and away from you, and because the bivy sack is tapered at the feet.

Finally, there’s the issue of length. Ultimate Direction specs a size regular FK Bivy at 82″ in length. It’s just not so. The one they sent me to review is 72″ long and weighs almost 25% more than spec.

The Hood

The FK Bivy’s hood is one of its distinguishing feature. While a self-standing hood is a nice luxury, it’s seldom necessary if you’re using a bivy sack with a tarp, because you can tie the mesh to a tent pole or prop it up from the inside to suspend it over your face.

The exterior of the FK Bivy’s hood is bug proof mesh. Additionally, there’s a solid piece of fabric that you can zip down over the mesh to block wind or dust from coming through it. When not in use, the solid fabric can be tied back, although it has a tendency to fall back down.

The hood is held up by two wire rods which are looped together for transport
The hood is held up by two wire rods which are looped together for transport

The hood is held up by two flexible wire rods that slip into four sleeves in the hood. Once inserted the rod is held in place with a small strip of fabric with snaps, that loops over the rod and snaps back into itself, holding the rod in place.  The rods are also tipped with plastic caps to prevent them from cutting through the base of the sleeves.

Unfortunately, the hood is fragile. If you tug too hard on a snap, it tears out of the fabric strip, making it impossible to keep the rod inserted. Further, when one of the end caps falls off the rod, it slices right through the base of the sleeve, again rendering the hood area useless. These are serious durability flaws, inflicted just after a few nights of use, so I’d caution you against putting too much faith in this product.


While it’s exciting to see a mainstream company developing ultralight gear for trail runners and fast packers, the Ultimate Direction FK Bivy isn’t ready for prime time. It’s too small, too difficult to use, and falls apart after light use. Reinventing the wheel is all fine and good, but this product is a flat.

Ultimate direction provided the author with this product for review.


  1. Holy moly! All I can say is thank you Philip for publishing honest reviews of products. This bivy sounds like a real dog. You wouldn’t know it by reading the endorsements of UD’s ambassadors.

  2. So I think I’m hearing you say that you don’t like this bivy much…

  3. You, too, can be a beta tester for our products! Just send a small amount ($180) and we’ll have a uniformed courier deliver the newest, experimental bivy sack right to your door.

  4. I think the MontBell Breeze Dry-Tec U.L. Sleeping Bag Cover would be a better choice, and is lighter on my scale. It is more of a “cover” than a “bivy” since it only has a drawcord closure vs a zip+bug net head area. I use it with a polycryo groundsheet. How do you think they compare Philip?

  5. There are lots of great products from small companies in this space – MLD, Borah Gear, Ti Goat, etc. The only problems with them are sometimes mediocre stitching quality and (definitely) shipping lead times.

    So it’s fine that this mainstream company tries to get into this kind of stuff–they’re probably able to reach an audience those small guys never will, and a lot of the people who buy from cottage companies do it because they like buying from cottage companies–but it’s funny that they don’t take more cues from the (extremely simple) successful, small scale products that have been out there for years. That tendency to over-engineer everything gives me a headache.

  6. Two better options:

    • MLD Superlight Bivy (a Section Hiker Gear of the Year winner)
    • Enlightend Equipment Recon Bivy

    I use the Recon under my MLD Duomid, and love its roominess and the top centerline zipper access and expansive mesh panel that provides great ventilation.

  7. I got one (long) in 2019 because I wanted to watch the summer clear skies.
    First night and I broke the snap pinched in the same super thin fabric (you need to pee etc. so open/close the snaps do happens). I first though about a velcro strip but finally repaired it with a Cordura (thicker) strip and super strong magnets. (required sewing machine).
    When dismantling, one plastic cap on the rod left its place but luckily I could find it in the grass and (super)glued it later.
    These “bugs” could have been easily avoided so overall unacceptable for the price: not field tested and designed for cost.
    Yet, the original idea and design are good for my purpose: Its breathable, you can see the sky and It keeps you warm with a fleece/thin sleeping bag+thin mattress+light anti-moisture sheet (underneath): I will stick to my customized/fixed bivy (now worth 100$ more if you include my workmanship!!).
    Go for It if you can fix/strengthen it before the field and follow the same purpose.
    Value for money? This is the last time I open my wallet for an ultimate direction product. The brand clearly designs for cost and non-durability: they should hire a quality engineer and fire the design-for-cost one.

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