Greylock 4 (0F)

(5 customer reviews)


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

  • Length: 56 inches (1.4 m)
  • Width: 42 inches (1.22 m)
  • Loft: 3.5 Inches (10 cm)
  • Weight: 22 oz. (0.62 kg)

Over-stuff: 25% over-stuff included!

Compression Sack: For 0 degree quilts we recommend the large size compression sack.

1 in stock


The Greylock 4 torso length under quilt is a 4 season version of the Greylock 3. The Greylock 4 is designed with current state-of-the-art features and is intended for the hammock user who is seeking an ultralight approach to bottom insulation. It is a dual differentially designed quilt and has body contouring radial baffles. In use the Greylock under quilt is effortless to attach and it will maintain its loft under any conditions. The Greylock 4 under quilt comes equipped with full length, channeled shock cord suspension that allows the user to make minor adjustments to their under quilt position. For those desiring to use the traditional JRB corner under quilt suspension the Greylock also comes equipped with corner mounting tabs. When filled with 800 fill power down this torso length under quilt weighs just 22.5 ounces.

Over-stuff: 25% over-stuff included!

All Jacks ‘R’ Better quilts are over stuffed by at least 25%. We do not recommend additional over stuffing. If you think you need additional over-stuff consider purchasing the next warmer quilt model.

Compression Sack: A lot of folks no longer use compressions sacks and instead keep their quilts dry inside a lawn contractor bag or trash compactor liner.  We do not want anyone to have to pay for something they do not want so now we offer them separately. For 0 degree quilts we recommend the large size compression sack.


Note: Torso length under quilt users typically use their sit pad or back pack as foot and lower leg insulation.

Activ-dri down™ – Activ-dri™ is a hydrophobic down treatment that keeps the down drier, while having no adverse effects on loft, fill power, or warmth retention. Activ-dri down is still down insulation and should be protected from direct exposure to moisture. All types of insulation, whether down or synthetic, will degrade in insulation capability if wetted.

5 reviews for Greylock 4 (0F)

  1. binfordw

    Great quilt. This is now my main “deep winter” UQ, I’ve used it down into the single digits without worry. Thanks for a great product

  2. Trevor (verified owner)

    Perfect quality, easy to set up and very warm. Doesn’t take up much space in the pack.
    Easy to vent in case you get too warm.
    I highly recommend JRB.

  3. DCBerry (verified owner)

    Absolutely the best out there was down to minus 38F with windchill and no problems under me! I really like the attention to detail as well!!! Thank you very much!!! BTW I bought mine just over a year ago and figured I could now do a proper review.

  4. Paul Casey

    Fairly new to the hammock world, but I thought I try a partial quilt after all of my research on hammock forums and various websites. So glad I went with a partial. I’m 6’1” and around 185 lbs. I tend to move a lot as I sleep and consider myself a cold sleeper (can only use my xlite down to mid 30’s). I was worried I’d need a wider quilt, but this is plenty wide even when I flip back and forth on my sides in the ol figure 4 position. Used it on three trips with temperatures between high 30’s to low teens. Was never too hot or cold. I used the 1/4” sleeping pad from arrowhead equipment for my feet. I cut it to about upper mid calf for length and have it wide enough to wrap almost all the way around on the inside of the quilt so when I flip flop I still have insulation underneath my feet/calves. It’s surprisingly comfortable. So if you’re worried about the quilt only being a partial and not extra wide (48”) don’t unless you’re just a thick dude. I don’t think I saved any weight compared to a full length because of the addition of the pad, but saved on interior volume in the pack. My feet aren’t constrained (tried my wife’s full length underquilt and didn’t like that feeling of the suspension pulling my feet towards the centerline of the hammock) and get a great seal for the turshiary suspension by myself because I can reach the adjustments from the hammock #SBO. It’s not the lightest underquilt. 20d fabrics and 800 fp aren’t cutting edge, but I don’t have to baby it like my wife does with her zeppelin and I didn’t feel guilty buying it at the $200 price point. Shug was a big reason why I went with this underquilt and has a great video on it. You probably already know that though if you’re still reading this monster of a review.

  5. Joey

    I bought this and I have used my Greylock 4 in the winter on my hammock many times and it keeps me warm. As a matter of fact, the first time I used this was at about 11pm deep in the wood in the White Mountains in very deep snow.
    I had never slept out before in my hammock and this under quilt, but I had watched plenty of videos so I knew what I was doing, and then it was time to put all the video knowledge into action.
    I hooked up this under quilt, laid down, relaxed and next thing I knew I woke up and the sun was up. It was exhilarating and exciting. This really does keep you warm in the winter in the snow and it not tough to hook up.
    The lack of full length has not been an issue for me at all during my many trips into the woods with this. I am very happy with this item, and would buy it again if I needed too.
    Not only do I use it in the winter, but also in the fall and spring, and it works.
    It is luxury in the woods.

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