Greylock 3 20° Three-Season 3/4 Hammock Underquilt

At 17 oz, the Greylock 3 is JRB's lightest 20°F hammock underquilt — a 3/4 underquilt for hammock campers who want the lightest possible bottom insulation without giving up a 20°F rating. 850FP down, dual differential cut, full-length channeled shock cord suspension included.

Built for Ultralight Hammock Campers Who Want 20°F Bottom Insulation at the Lowest Possible Weight

The full-length Mt Washington 3 covers you from head to foot. The Greylock 3 covers what matters most — your torso and hips — and saves the weight that would otherwise go to covering your lower legs and feet. At 56 inches long, it runs from your shoulders to your knees. Most users pair it with a sit pad or a back panel from their pack underneath their lower legs. The result is full 20°F bottom insulation where it counts, at 17 oz — nearly 3 oz lighter than the full-length version. If you're an ounce-counter who already carries a sit pad and wants the most efficient bottom insulation setup possible, the Greylock 3 is the right call.

How It's Built: Dual Differential Cut, 850 Fill Power Down, 1.1 oz Taffeta Shell

The Greylock 3 uses Dual Differential Contoured Radial Baffles — the same construction as the full-length Mt Washington series. The inner shell is cut smaller than the outer shell so the quilt conforms naturally to the curved underside of a hanging hammock without the two shells pulling together at the edges and compressing the down. Every baffle stays full and lofted regardless of how the quilt hangs. This is why a differential-cut underquilt performs at its rated temperature when a flat quilt hung beneath a hammock would leave you cold.

The Greylock 3 is filled with 850 Fill Power RDS-certified down. Fill power measures how many cubic inches of loft one ounce of down produces when fully expanded — at 850FP, the Greylock 3 achieves its 20°F rating with less fill by weight than underquilts built with lower-grade down. Every Greylock 3 ships with a 33% overstuff by weight, so it holds its rating even as the down accumulates oils and dirt between cleanings and loses loft.

Suspension is full-length channeled shock cord with adjustable ends and corner mounting tabs for users who prefer the traditional JRB corner suspension method. Cinch the ends to seal against the hammock on cold nights; loosen to vent on warmer nights. Setup takes under a minute on all gathered-end and bridge hammocks — ENO, Hennessy, Warbonnet, Dutchware Chameleon, and most DIY builds.

The shell is 1.1 oz taffeta with a DWR coating. Every Greylock 3 ships in a storage bag that does not compress the down — keep the quilt in it between trips for long-term loft preservation.

Named for the Trail

Mount Greylock, at 3,491 feet, is the highest peak in Massachusetts. The Appalachian Trail crosses the summit, where clouds collect even on clear days in the valley below. The summit is exposed, the temperatures drop fast after dark, and the shoulder seasons bring the kind of damp cold that feels colder than the thermometer says. Spring thru-hikers push through Greylock in April and May — early enough that nights can still drop well below freezing at elevation.

The Greylock 3 carries that name because it was built for the same principle: carry only what you need, but make sure what you carry does the job. Torso insulation where you lose heat. A sit pad for the rest. Nothing extra.

Handmade in Pennsylvania by Jacks R Better — making quilts since 2004. In-stock quilts ship the same or next business day.

Specs: Greylock 3 20°F 3/4 Hammock Underquilt

Note: 3/4 underquilt users typically use a sit pad or pack back panel for foot and lower leg insulation. For full-length coverage, see the Mt Washington 3.