Mt Washington 4 (0F)

(15 customer reviews)


Comfort rated to 0° F (-17° C) the Mt Washington 4 is a dual differentially designed winter underquilt with body contouring radial baffles.

Mt. Washington 4 Winter UnderQuilt
Length: 77 inches (1.8 m)
Width: 42 inches (1.07 m)
Weight: 28  ounces (0.79 kg)


3 in stock


Winter Hammock Underquilt

To tackle the worst winter conditions, Jacks ‘R’ Better has designed the best winter 0 degree hammock underquilt. Featuring a dual differential cut, body contouring design, and constant height radial baffles to achieve a 0° comfort rating. As a result, these are the most capable and warmest available hammock underquilts.


  • Hammock Fit –The Mount Washington 4 0 degree winter hammock underquilt works on all gathered end and bridge hammocks. Such as ENO Hammocks, Hennessy Hammocks, Warbonnet Hammocks, Dutchware Chameleon, and most other brands and DIY hammocks.
  • Down 850FP: Fill power is a measurement of how much space one ounce of down will occupy when lofted, measured in cubic inches.
    • Since the temperature rating of a quilt is based on how much loft there is, quilts using a higher fill power down will require less down by weight to achieve a specific temperature rating than a bag using a lower fill power down.
  • Overstuff: All Jacks ‘R’ Better winter hammock underquilts are optimized with a 25% over-stuff. Markedly reducing down migration and enabling the quilt to maintain its rating if the down loses loft between cleanings. Consequently, we do not recommend any additional over-stuffing.
  • Long-Term Storage: All Jacks R Better hammock Underquilts come in a zippered storage bag that does not compress the quilt and allows airflow. Consequently makes it perfect for long-term quilt storage.
  • Packing: We recommend using a lawn contractor bag or trash compactor liner while backpacking to keep your hammock underquilt dry while allowing it to expand or compress to fill available space in your backpack evenly.  Additionally, we offer compression sacks separately for individuals looking to pack their quilt into the smallest space possible.



15 reviews for Mt Washington 4 (0F)

  1. Thomas Vickers

  2. Rick Allnutt

  3. Chuch Carnes

  4. Andrew Morgan

    New to hammock camping. I did extensive research and ended up choosing this product. I took my under quilt out of the packaging 10 minutes before setting up camp at midnight. I promptly installed the under quilt incorrectly. The gusty 20 degree mountain air gave me a bit of a cold back and butt. Night number two brought the same conditions, and this time I took time to install the under quilt correct…. best/warmest sleep I have ever had outdoors. Period. Excellent product. Great customer service. Fast shipping. Made in the USA. Can’t wait to do some deep winter camping with this.

  5. Robert Waugh

    Broke out the hammock gear last night. Temp was 30 deg. The mt Washington under quilt kept me warm all night. Thanks for a good nights sleep. Great product

  6. Thomas Feliciano (verified owner)

    I bought this underquilt for my App Trail thru hike in 2015. The 4th night I was out (March 3rd or 4th) it began raining ice and blowing snow. In a matter of an hour it went from a pleasant hike on the mountain to a dangerous ice blizzard. After what seemed like forever I got my hammock up (being the wind was blowing like mad and my fingers were numb it took a bit). Once the hammock was up I easily put the underquilt on and crawled into my hammock. I was cold and somewhat terrified as my hammock was swinging from side to side with the intense gusts of wind. This underquilt kept me from getting severe exposure. The wind did cause some cold spots which made me need to reposition myself every few minutes, but otherwise I was warm.

    I used the quilt for another 2 months and every night I was warm and comfortable even in lousy weather. As the weather got warmer I sent the quilt home (its a bit bulky and I was going ultralight (12-15lb pack) at that point). I went thru 4 lightweight sleeping pads (to fight off cold butt syndrome), trying each one out and sending it home. I ended up settling for an exped synmat. None of them were as warm and comfortable as this underquilt. This year Im just gonna order a lighterweight quilt and ditch the pads. You just cant beat them.

  7. Scott Zuziak (verified owner)

    Just got my Washington 4. Researched a lot of quilts and finally pulled the trigger on this quilt. Great customer service and the quilt is toasty warm and very light. Highly recommend. Thanks Jack.

  8. Tim Williford (verified owner)

    To me customer service is every thing, that being said Jack was so supportive with all my questions, I have a Lawson blue ridge hammock and the quilt with Jacks help works great. If your looking a under quilt look no further, this quilt is high quality and very very warm.

  9. Bill Kline

    This review is quite late, as I got the MW4 UQ several years ago. I had given it an extensive review over at one of the hammock forums, but I did not remember to also review it here. So I will do so now.

    This was my first UQ, one of their very first models with untreated down.

    A summary of cold weather use:
    1:Placed on the War Bonnet Black Bird hammock. This proved to be far more involved than using it on the JRB bridge hammock. Still, following the directions, and making a few tweaks here and there, it was accomplished, or at least appeared to be so. Now this night was no real test for the quilts temperature rating, it only got down to 18°F. However, it was very windy, and since I was in the backyard I could not really seek out a sheltered location. And those high winds did seem to shift around quite a bit during the night, coming from different directions. So sometimes my large tarp did a good job of blocking the wind. other times, I think maybe it did not. Sometimes my hammock was swaying in the wind, either from the wind hitting the hammock or the stand, don’t know. But either way, my back, butt and legs were toasty warm all night. So I’ll have to call that one a total success, below 20F/high winds.

    2: Next( and all following) test was on a JRB BMBH(bridge hammock). I had left the hammock and quilts out all night, and the temperature dropped to 27F. I did not sleep out that night, but I woke up a bit before 5 AM and decided to go out and give it a try. I found my tarp, top quilt and under quilt all covered in a thick layer of frost. So I replaced top quilt with a dry one from in the house, but left the under quilt as it was, and crawled in. I stayed there for a few hours, and though it took me a bit longer than usual to warm up(not surprisingly considering the frost covered under quilt that was probably the same temperature as the air), before too long I was once again nice and warm.

    3: Next test was on a February, very rainy (turning to about 5 inches of snow), backpack/ group hang in the Sipsey wilderness of North Alabama. I believe it dropped once again to about 27°F as the rain turned to snow. I think it might’ve been around 2 or 3 AM that I had to get up to pee and I realized that I was a little bit on the cool side. My long/wide down top quilt only weighed 21 oz, so it was not good for temperatures much below 30F, that’s for sure. Although I did have on some warm clothing, a fleece cap covered with the hood of my thin(12 oz size extra large) synthetic jacket. But, I had with me a separate down hood. I put it on and crawled back in, and quickly warmed up and was toasty warm the rest of the night. Another total success as far is this under quilt went.

    4: Finally, my only real test anywhere near the quilts temperature rating, though I still did not manage to get down to zero. By the time I crawled in about 11PM, the quilts and tarp were once again covered with frost! Not exactly a fair way to start a test. We made it down to about 11F. I wore my usual warm clothing. I had some top warmth issues through the night, and the TQ got soaked with condensation in the layer near my neck/chin. At some point I replaced the TQ with an old synthetic bag rated for 5F, used as a TQ when on my side, but I got in the bag when on my back so the hood would not be in my face, and had luxurious warmth after that, either way. My back was nice and warm the entire night.

    So there you go, this UQ has always kept me warm near or above the rated temps. And it does not weigh much and compresses quite nicely. It would be hard to beat this quilts performance IMO.

  10. Joshua Viola

    This review is long overdue. I heard about JRB from a friend and after agreeing to go winter camping, I decided to start looking into one. After speaking with Jack Tier a few times, I decided to go with the MW4 with 2oz overstuff and the active dry. I ran this UQ with a HH Deep Jungle XL on a winter advisory weekend in the Seneca Rocks National Recreational Area. It quickly dropped into the single digits after our arrival, and probably below zero with wind chill. Living most of my life in the south, I was not used to this kind of cold. Every liquid not on the fire ring froze in minutes. BUT I slept VERY warm and even had to vent out some heat at times. The UQ was very warm and its design fit my hammock perfectly with very easy setup even with gloves on. I cannot give enough praise of the MW4 and I look forward to trying other JRB products in the furure!

  11. “Martian”

    just finished 3 ridges wildernss temps were in the 20’s at night .. the mt washington 4 and hennessy expidetion drew alot of attention at the shelters and i could feel some of the envy. quilt was extreamly warm and im 100% sure i had the best night sleep out of everyone out there. only problem i had with it was i didnt want to get out of it.. i orderd and picked up in store it was really cool to see all the gear in person outatanding products and service … at 5’5 i can use it as a blanket and i plan to on family tent trips. .

  12. Larry Shepler (verified owner)

    Used my Mt. Washington 4 twice this past week. On the first outing it snowed and temps dipped to 3.9F. On that night I did not stack under quilts, and the Mt. Washington was very warm in a Chameleon. On New Years Eve, i stacked the Mt. Washington with another UQ (ENO Blaze) in order to break the wind and provide some protection to the Mt. Washington. Temperatures lowered to -16F with a breeze blowing at a steady 10-15 mph. The combination of two UQ completely blocked the cold on my underside.
    I have used the Mt. Washington on 10 or 11 outings since I got it, and I have been very, very pleased with its performance. I would highly recommend this UQ to anyone with low temperature needs.

  13. shop (verified owner)

    This quilt has full more than full coverage for a 6′ human, is incredibly warm and is very well built! Thanks JRB!

  14. Raven

    Simply put, this is one terrific underquilt. I’m a cross-country bicyclist that’s been traveling the country for The last 5 years. And have been constantly been updating and modifying my sleep system.

    The first night out it kept me nice and toasty warm I warmed up evenly and quickly, and the ease of installation was really nice. I didn’t have to fiddle around making a bunch of adjustments, and more importantly it kept me warm.

    As a cross-country bicyclist slash nomadic bicyclist I am always looking to lighten my load and make my packing of my home and unpacking of my home easier. This new quilt completely removed a synthetic 20 degree quilt in ways absolutely nothing and stores away easily.

    Thanks Jack’s r better

  15. Kristen

    My JRB quilts have kept me warm on three camping trips now. I was cozy through several nights of sub-freezing temps and lots of wind. They are more than just functional; they’re downright luxurious. Love them and look forward to many more nights with them.

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