Greylock 3 (20F)

(11 customer reviews)


Conservatively rated to 20° F (-7° C) the Greylock 3 is a dual differentially designed underquilt with body contouring radial baffles.

  • Loft: 2.5 Inches (10 cm)
  • Length: 56 inches (1.4 m)
  • Width: 42 inches (1.22 m)
  • Weight: 17 oz. (0.48 kg)

Over-stuff: 25% over-stuff included!

Compression Sack: For 20 degree quilts we recommend the regular size compression sack.

Out of stock


  1. The Greylock 3 torso length lightweight underquilt 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 lightweight underquilt and has body contouring radial baffles. In use the Greylock underquilt is effortless to attach and it will maintain its loft under any conditions. The Greylock 3 lightweight underquilt 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 underquilt suspension the Greylock also comes equipped with corner mounting tabs. When filled with 800 fill power down this torso length under quilt weighs just 17 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 20 degree quilts we recommend the regular size compression sack.

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

The Greylock 3 torso length lightweight underquilt works on ENO Hammocks, Hennessy Hammocks, Warbonnet Hammocks, Dutchware Chameleon, as well as most other brands and DIY hammocks.


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.

For a full length version check out the Mt. Washington 3 20° Underquilt.

11 reviews for Greylock 3 (20F)

  1. SkunkApe

    I have been using this quilt (900FP) all season in the South East of the USA. From Florida to North Carolina and in sub freezing weather. I am an ultralighter with a base weight of 8.5lbs with a Shenandoah to match. I LOVE THESE quilts.

  2. topwaterfrogger

    Bought one this year, use it on my Hennessey hammock and it works great. Wasn’t sure I was going to like the torso length but it does the job. Coldest I’ve been in yet was 34 degress and I was warm all night. I also have a JRB top quilt. I’m an ultralight backpacker so weight is always important.

  3. Earl Gunn

    I have the Greylock 3 and the seirra sniveler. And love them. We went camp at hogs camp gap back in February 2015 it was 7 degrees over night and they work pretty well for being rated at 20 ish. Needless to say they make a great product.

  4. Steve (verified owner)

    Just got back from a Sierra snow shoe trip. Took the Greylock down to 21 degrees. Accuweather said 12 degrees “real feel”. Impressive how the torso length is sufficient to keep warm. I had a 2x2ft section of reflectex under my feet and stayed comfortable. Granted each time I reached forward to knock snow off the tarp, I let a little cold air in, but it didn’t take long for the heat build up again and get comfortable. Gotta make sure you keep the under quilt suspension over your outside shoulder and feet!

  5. Lathan Deyoung

    Love this under quilt. Got it last spring for a trip to pictured rocks in the u.p. Got down into the low 30s one night with high winds and heavy rain. Was warm all night. Woke to find my tarp was dripping on the side of the quilt, but the water just beaded up and ran right off. Quilt was perfectly dry. This is not the last jacks r better product I will buy. Want a full length for colder weather. If your not looking to save weight I would go that route.

  6. John (verified owner)

    I used my Graylock 3 this weekend for the first time in the mountains of northwestern VA. Low temperature on Friday night was in the mid-high 20’s with 15 mph winds most of the night. At first, I was hesitant about not having a full-length under-quilt, but my 20 degree bag (with fleece liner) was perfect. I stayed warm all night. Great product, great customer service, and I highly recommend it!!!

  7. brent (verified owner)

    Wow, I can’t believe how good this quilt is. Decently priced, takes up almost no room and weighs next to nothing. These guys know what they are doing.

  8. Valveless

    I now own 3 torso-length underquilts for my wife, etc and the Greylock is the one I now grab for myself. Have used it since the beginning of the summer (thank you Trail Days sale!!) in weather ranging from overnight lows in the warm 60s (Havasupai), the damp and foggy 40s (Pt Reyes), and the brisk 30s (High Sierras). The size is perfect for my 5’10” frame such that I don’t bother with anything additional insulation under my feet. I’ve also not yet bothered to install secondary suspension prusiks as the quilt stays well enough put, shoulder to ankle, that I haven’t yet seen the need. Perhaps for winter. The only thing I **don’t** like is the .9 oz fabric — too slinky and soft for my taste. I much prefer the 1.3oz used for my Sniveler and didn’t realize the different spec until the UQ showed up. I should add, this is merely an aesthetic preference. The downproofness is just fine and I have no concerns about durability.

  9. Vanhalo (verified owner)

    I have used the 56″ Greylock 3 (+1 oz.) for over 90 days now in temperature ranges from 13°-64°. and it hasn’t failed me yet.

    My initial purchase was motivated in part by a thru-hiker who used it for the entire AT.

    I am almost 5′-11″, 180lbs.

    I use an 12 x 16 inflatable footpad for my feet and a folding sit pad behind my head.

    This is my favorite JRB product next to their summer blanket which are always used in tandem.

  10. Elijah (verified owner)

    Had high expectations for this quilt as they claim it’s conservatively a 20 degree rating. And that’s accurate on the bottom. Because of the way the baffles are the down migrates to the bottom. Meaning the sides are left really cold. Had it out in 45 degree breezy day and my shoulders and hip were cold. Secondly, maybe it’s my inexperience with partial underquilt a but there were cold spots all the way down below my waist. Hips and thighs never could get warm due to the cold spots. Still going to play with the suspension to see if I can adjust it but overall not satisfied with it.

    • thejacks

      Hi Elijah! We can help get your quilt working correctly. The down should not migrate beyond your sides. Below are some tips for getting the correct hang. If you need additional assistance, please give us a call.

      1.Shake out the quilt to distribute the down before hanging it.
      2.Hang the quilt tight enough that it lifts the hammock when no one is in it.
      3.Grab the corners of the quilt on either side of the hammock and pull away from each other to ensure the quilt is not bunched up along the suspension. The cord locks will hold it in place once it is setup.
      4.If you lay at an angle in your hammock it may be necessary to have the quilt set at an angle long the suspension also to ensure proper coverage.
      5.Pull the end drawcords just enough to seal the ends off when you are in the hammock. Pulling them too tight can cause air gaps
      6.Be sure that the suspension runs over you. If it passes under your legs or shoulder it will push the quilt away from the hammock and cause a very large air gap.

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