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Speer Hammocks Frog Sac Sleeping Bag REVIEW

Warm weather, full-length center zip, PrimaLoft insulated sleeping bag.


by Carol Crooker | 2005-10-11 03:00:00-06


Speer Hammocks Frog Sac Sleeping Bag REVIEW - 1
Speer Hammocks Frog Sac multi-use sleeping bag.

The Speer Hammocks Frog Sac is a well-constructed PrimaLoft insulated sleeping bag rated to 45 °F (7 °C). The most notable features of the Frog Sac are the full-length center zipper, foot opening, semi-rectangular outline, and locking toggles at the foot and neck openings. These all combine to allow the Frog Sac to be used in various ways. The bag can be fully or partially opened and used as a quilt. You can wear it as extra insulation in camp. While wearing it, you can open the bottom and unzip the zipper from the bottom to create as much room as you need to walk around or to get up from a sleeping pad or in/out of a hammock. For any camp chores you must unzip the front of the bag to free your arms and hands, letting in cold air. At the bag's 45 °F (7 °C) rating, the Frog Sac is warm enough as a camp robe as it is designed, but arm openings would be a nice option and make it useful as in-camp insulation below the bag's rating.

At 1 pound 11.5 ounces (780 g), the Frog Sac is not among the lightest summer weight synthetic insulation sleeping bags and quilts, but its versatility over a simple bag or quilt may make the extra ounces worth it for users interested in a bag they can also wear in camp for insulation.

In Brief

  • PrimaLoft insulated
  • Full-length center zipper
  • Drawcord foot box closure
  • Shaped shoulders
  • Minimal hood
  • Locking toggles at the foot and neck openings



Speer Hammocks, Inc.


Frog Sac


Semi-rectangular, full front zip with drawstring foot and neck closures

Size medium tested

Medium, length 6'10" (208 cm) measured, 7' (213 cm) claimed. Large, length 7'6" (229 cm) claimed.


SizeManufacturer Specification shoulder/hip/foot in (cm)Backpacking Light Measurement shoulder/hip/foot in (cm)
Medium60.5/-/- (154/-/-)60.5/60.5/40.0 (154/154/102)
Large64.5/-/- (164/-/-)-


Backpacking Light measured 1 lb 11.5 oz (780 g), size Medium; Manufacturer claims 1 lb 10 oz (737 g) for size Medium, 1 lb 14 oz (850 g) for size Large. Stuff sack adds 0.8 oz (23 g).

  Fill Type

Synthetic, PrimaLoft


Backpacking Light measured single layer loft 0.5" (1.3 cm)

  Manufacturer's Rating

45 °F (7 °C), 50 °F (10 °C) for a cold sleeper

  Outer and Liner Material

Outer is ripstop nylon with breathable DWR coating 1.1 oz/yd2 (37.7 g/m2); Liner is ripstop nylon 1.1 oz/yd2 (37.7 g/m2)




Full-length front zipper with two sliders


Insulated zipper draft tube, tailored shoulders, contoured hood with drawstrings, bottom foot opening with drawstrings, locking barrel toggles on drawstrings

  Model Year



$99 medium, $109 large


The Frog Sac has PrimaLoft fill and 1.1 oz/yd2 (37.7 g/m2) ripstop nylon for the outer and inner shells. The outer shell has a DWR treatment. The top and bottom layers of the bag are each approximately 0.5 inches (1.3 cm) thick when fluffed up. The fabric is very comfortable against the skin, and the bag drapes closely on the body rather than having a stiff feel. The front and back sides have four horizontal sewn-through baffles spaced 17 inches (43 cm) apart. The corners of the squares on the back of the bag formed by the single vertical baffle and the horizontal baffles are not sewn through to reduce heat loss in those areas.

The Frog Sac is closely cut at the shoulders with a 60.5 inch (153.7 cm) girth. The girth of the bag remains the same until it begins to narrow just above the knees - still allowing plenty of room for your knees to maneuver in the bag. The shoulders of the Frog Sac are shaped rather than tapered as in a mummy bag. They are designed to help keep the bag on your shoulders while you are wearing it.

Speer Hammocks Frog Sac Sleeping Bag REVIEW - 2
The Frog Sac's simple hood and locking toggles.

Wearing the hood holds the bag up when using the Frog Sac as a robe. The unshaped hood is formed by sewing the top and bottom layers of the bag together in an envelope style with the seam on the outside. It is very minimal, yet adequate for a summer weight bag. There are no extra pieces in the hood to form it into a "head" shape. When sitting or standing, the front edge of the hood rests uncomfortably a couple of inches forward of the crown, rather than on your forehead. The hood stays in place when wearing the bag as a robe or sleeping in it and turning side to side.

The Frog Sac has a full-length YKK #5 center zipper with two, two-way sliders. Anti-snag tape covers the insulated zipper baffle. Both the foot and neck openings have draw cords with toggles that can be snapped together. The locking barrel toggles can be used to secure the bag when wearing it as a robe. The top toggles allow you to fasten the bag on your shoulders so it doesn't fall down when you are wearing it without the hood. The bottom of the bag can be flipped up (or under) and held in place at your waist with the bottom toggles so you can move about camp. The toggles and zippers are easily adjusted with gloves on.

The Frog Sac can be rolled and folded to fit into its stuff sack or simply stuffed. It is a close fit but it is not overly difficult to stuff the bag. The stuff sack has two draw cords 1.25 inches (3.2 cm) apart. The inner draw cord is intended to help stuff the bag into the stuff sack, but instead hinders stuffing by tangling with the outer draw cord.

The Frog Sac weighs 1 pound 11.5 ounces (780 g). There are several synthetic bags and quilts rated the same or colder that weigh less (e.g. Fanatic Fringe quilts, The North Face Propel bag). The Frog Sac is not the lightest synthetic summer weight sleeping option, but its suite of features are matched only by Integral Designs PrimaLoft Poncho Liner (Prima Blanket) which is of comparable weight.


Speer Hammocks Frog Sac Sleeping Bag REVIEW - 3
The Frog Sac and the 5'10" (178 cm) author - a couple of inches (5 cm) to spare once the bottom is cinched shut.

The Frog Sac was tested in a range of conditions in Arizona and Washington state: 75 °F (24 °C) to 38 °F (3 °C), high gusting winds and still air, dry air and humid air, on the ground and in a hammock.

The Frog Sac creates a cozy environment with its PrimaLoft insulation and lightweight ripstop nylon shell, along with the insulated zipper baffle that helps block wind and hold warmth in. The outer shell has a DWR treatment that keeps spray and surface condensation from soaking into the insulation.

The torso is cut wider than some ultralight mummy bags (60.5 in/154 cm girth) with enough room for a person of medium build to wear a lightweight insulating top inside the Frog Sac. The semi-rectangular cut leaves plenty of room for your knees, and your feet won't get claustrophobic with the 40 inch (102 cm) foot girth and option to open the bottom of the bag. Speer Hammocks claims the bag is suitable for someone up to 6 feet (183 cm) tall and that is accurate. I'd recommend that if you are 6' 1" (185 cm) tall, you opt for the large model.

I had complaints about the hood when sitting, but it did its job while I was sleeping. It stayed on my head as I turned from side to side. I was able to fit a fleece hat on my medium to large head under the hood. Although the hood is minimal, it is adequate at the bag's temperature rating. The whole bag was comfortable to toss and turn in; the hood stayed in place on my head, and the bag fit closely enough that the center zipper stayed in the center. The bag has the soft comfortable feel of an old blanket.

The full-length zipper is the right weight for the job. It operated smoothly for the most part (I had difficulty aligning the zippers to reconnect the two halves of the bag after having it laid out flat on two occasions). Anti-snag tape covers the insulated zipper baffle and with care, allows snag free zipping.

The Frog Sac can be turned into a roomy 5 foot (152 cm) by 6 feet 10 inch (208 cm) top blanket. A foot pocket can be formed by partially closing the full-length zipper if desired. The center zip puts the hood at your face when using the Frog Sac as a quilt, but the hood is small enough that it doesn't get in the way. The shaped shoulders hook the blanket onto your shoulders when you are on your back so that the bag stays tucked under your chin.

The Frog Sac can be used as an insulation layer in camp, but you'll have to unzip the bag nearly to your waist if you are using your hands. Cold air comes in, but near the rated temperatures, supplementing the Frog Sac with a light insulating top is enough to keep me warm. Wearing the hood keeps the Frog Sac from slipping down, or when not wearing the hood you can use the locking toggles to secure the bag around your neck. When wearing the hood, the shoulders of the Frog Sac rest about half a foot (15 cm) above your shoulders so your head supports a lot of the weight of the bag. Since the hood is an envelope shape rather than conforming to your head, the weight on your head is concentrated on the front seam of the hood, which can be uncomfortable.

Speer Hammocks Frog Sac Sleeping Bag REVIEW - 4
The Frog Sac as insulating camp wear you can move around in.

The Frog Sac's bottom closes with draw cords and toggles. Sitting in camp, the zipper can be fully zipped with just the bottom open for your feet. It is surprisingly warm encased in this barely 0.5-inch (1.3 cm) single layer loft bag. To change to sitting cross-legged, or to make legroom for standing up and walking around camp, the bottom can be partially unzipped. The bottom edge of the Frog Sac can be turned up and secured around the waist with the locking toggles so that you can even set up or take down camp while keeping warm in the Frog Sac. The full-length zipper that opens from the bottom and locking toggles are the strength of the Frog Sac. These features allow you to easily go from standing to sitting, from laying on the ground, to up and walking around and it is a warm luxury to be able to get in and out of a hammock still carrying your built up warmth around you. Midnight calls of nature can be accomplished still partially encased in your warm bag although armholes in the bag would make this skill much easier to master.

Missing from this review (and for all sleeping bag reviews published here, for that matter) will be an assessment of whether or not the sleeping bag performs adequately at temperatures near its manufacturer-reported temperature rating. Click here for the complete Backpacking Light Position Statement on Sleeping Bag Temperature Ratings.


The Frog Sac is durable enough for normal use. Stitching is evenly spaced and straight; the seams are not likely to start opening. The outer shell fabric is prone to runs although this does not affect function. The zipper is the right size for the job. A smaller zipper would save weight but might not be up to the stress put on the zipper when wearing the bag around camp. I dragged the bottom of the Frog Sac around when walking and sitting on the ground in camp; it shows no signs of wear.


The Frog Sac is a carefully built bag with appropriate materials and techniques used in construction. The size medium Frog Sac retails for $99. This price is comparable to other summer weight synthetic bags. The Frog Sac does its job as a sleeping bag, and offers many extra options for use with its full-length center zipper and bottom opening which add value.

Recommendations for Improvement

  • My number one recommended change is to add another section to the hood so it fits the head better and distributes the weight of the bag (when wearing it as a robe) over a larger percentage of the head for more comfort.
  • Armholes would make it much easier to wear the bag while using your hands such as when cooking or setting up camp.
  • Remove the second draw cord on the stuff sack, it just gets in the way and you'd save 0.1 ounces (3 g).


"Speer Hammocks Frog Sac Sleeping Bag REVIEW," by Carol Crooker. (ISSN 1537-0364)., 2005-10-11 03:00:00-06.