Greylock 4 0° Winter 3/4 Hammock Underquilt

At 22 oz, the Greylock 4 is JRB's lightest 0°F hammock underquilt — a 3/4 underquilt for winter hammock campers who want the most efficient bottom insulation setup possible. 850FP down, dual differential cut, full-length channeled shock cord suspension included.

Built for Winter Hammock Campers Who Want 0°F Bottom Insulation at the Lowest Possible Weight

The full-length Mt Washington 4 covers you from head to foot at 0°F. The Greylock 4 covers your torso and hips — where you lose the most heat — and lets you use a sit pad or pack back panel for your lower legs and feet. At 56 inches long and 22 oz, it delivers a true 0°F bottom insulation rating at nearly 3 oz less than the full-length version. If you already carry a sit pad and want the lightest possible winter bottom insulation setup, the Greylock 4 is the right call. If you want full-length coverage without the extra gear management, the Mt Washington 4 is the better choice.

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

The Greylock 4 is built with Dual Differential Contoured Radial Baffles. The inner shell is cut smaller than the outer shell so the quilt conforms naturally to the curved underside of the hammock as it hangs, without the two shells pulling together at the edges and compressing the down. The baffles run radially to follow the contour of your body, keeping loft height constant from head to foot. At 0°F, cold spots are not recoverable — the differential cut is what ensures every baffle stays full all night.

The Greylock 4 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 4 achieves its 0°F rating with less fill by weight than underquilts built with lower-grade down. Every Greylock 4 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 tight for a sealed hang on the coldest nights; loosen slightly to vent when the temperature allows. 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 4 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 the weather rolls in fast and the temperature drops well below what the valley suggests. In January, the summit sees sustained winds, icing, and temperatures that make a 0°F rating a requirement, not a margin. Northbound thru-hikers who push through Greylock in late May and June still find winter-like conditions at the top.

The Greylock 4 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 at 0°F. 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 4 0°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 4.