Western Mountaineering Megalite Mummy Sleeping Bag: Sleeping in the Clouds

WM MegaLite featured
Mark Foster
Written by Mark Foster

When you’re going camping or backpacking, you’ll want to bring some essentials with you. Of course, you’ll be bringing a tent or hammock, a backpack and food, but what about your sleeping bag? Sure, you know that you need one, but not every sleeping bag is designed with the same features.

Some sleeping bags are designed for the summer season while others provide you with 3-season use. Your goal as an outdoor enthusiast is to select a sleeping bag that suits your needs. With that being said, there are many options out there which can leave you overwhelmed with choices. We are going to review one of the best sleeping bags on the market, the Western Mountaineering Megalite Mummy Sleeping Bag.

Product Specifications

  • One of the most compressible sleeping bags
  • Made with high-quality lightweight materials; 850-fill goose down, 12D shell fabric
  • Continuous baffle system
  • Ultra breathable, high thread count ExtremeLite shell fabric
  • Water-resistant coating that protects the down from moisture, frost and spin drift
  • Interior nylon fabric that gives an extra cosy feeling

Check the price on Amazon

Let’s look a little further into what this sleeping bag offers its users.


Many campers and backpackers are looking for a sleeping bag that won’t weigh down their backpacks. Instead, they’re looking for a sleeping bag that’s lightweight. However, many are worried that if they opt for a lightweight sleeping bag, they’ll have to sacrifice warmth and comfort.

With the Megalite Mummy sleeping bag, it’s the ideal bag for those who need a lightweight, yet warm sleeping bag. Another issue with sleeping bags is that they aren’t designed for people who are above average height and weight. With the Megalite Mummy sleeping bag, it comes in 6” left zip and 6” right zip, so you’ll be able to fit comfortably inside this sleeping bag.

Let’s look closer at some of the features the Megalite Mummy has to offer.


If you’re looking for a compressible sleeping bag, the Megalite Mummy is one of the most compressible sleeping bags on the market. Though it’s highly compressible, you’re still given a large and roomy sleeping bag to lay in – a great balance of space and comfort while still being able to compress it into a small pack.

The stuff sack that comes included with the Megalite Mummy does a great job of compressing the bag, however, if you purchase a compression sack, you’ll be able to compress it down an extra 30-40%. So, if you’re going to be backpacking, the Megalite Mummy will be a light and non-bulky addition to your backpack, which is what you want.

In comparison to other 20-30F bags, the Megalite was the most compressible.

Design and Durability

The design of the Megalite Mummy is simple as it’s focused on creating a spacious interior, without adding bulk and weight. The bag is made with high-quality lightweight materials that aid in keeping the weight to a minimum. You’re not going to get a lot of extra features with this sleeping bag because that’s not what it’s focus is, but you’re going to be warm.

This bag is made with incredibly lightweight 850-fill goose down that’ll rock you to sleep like a baby. It’s made with a continuous baffle system that allows you to control where the down will be, letting you make the bag either warmer or coolers, depending on where you’re camping. That was a problem for many campers as they found themselves either overheating or freezing in their sleeping bags.

The full-length draft tube also helps prevent any breeze from entering between the zipper teeth, so you’ll be snug and secured in this bag.

When it comes to durability, don’t worry. Many people feel that because something is lightweight, it’s fragile. However, this isn’t the case. Rather, the Megalite Mummy is made with ultra breathable, high thread count ExtremeLite shell fabric that’s highly durable. It’s also designed with a water-resistant coating that protects the down from moisture, frost and spin drift. Where you travel to with this sleeping bag, it’ll be right beside you.


Nothing says comfort like the Megalite Mummy. Its whole concept is based on providing you with comfort and space. It’s continuously rated as one of the most comfortable sleeping bags and we completely agree. Its dimensions measure 64“ for the shoulders, 56” for the waist and 39” for the feet, so, overall, you’re given plenty of space inside your sleeping bag.

Because the bag is relatively large, you’ll be able to add layers into your sleeping bag, giving yourself extra warmth and comfort. If you’re a stomach or side sleeper, you’ll love this sleeping bag because you’ll be able to bring your knees up fairly high.

With the interior nylon fabric, you’ll be given an extra cosy feeling which everyone seems to love. If you’re not a fan of the mummy-style sleeping bags, then you have yet to try this sleeping bag out. It’ll convert you.


What do we have negative to say about the weight of this sleeping bag? We got nothing. It’s one of the lightest sleeping bags on the market, weighing 1 lb 8 oz. At this weight, this will be your lightest option in this specific temperature range.

Many of the other lightweight sleeping bags, unfortunately, are designed quite narrow which gives you a tight and uncomfortable sleep. However, you’re still given a spacious interior in the Megalite Mummy, even though it’s extremely lightweight.

Western Mountaineering Megalite overview

Another feature that attributes to its lightweight is the premium +850 down fill which still gives you the warmth you need however doesn’t drag you down. The lightweight 12D shell fabric adds onto the lightweight concept because of its high thread count which traps the insulation, maintaining a super-high warmth-to-weight ratio.

If you’re looking for lightweight, you cannot get any lighter than this. So, when it comes to weight, you won’t have to bat your eyes as this will never be an issue with the Megalite Mummy.


The Megalite Mummy is ranked quite high among outdoor enthusiasts specifically, for this reason, it’s extremely versatile. Whether you’re camping, cycling, backpacking, you’ll be able to bring this sleeping bag with you. You can throw it in the back of your car, go on week-long trips with it and on top of it, it’s light enough to use during the summer season.

It’s able to withstand -1 degree Celsius weather, so it’s ideal for 3-season use and possibly winter, depending on where you’ll be going. Another great feature about this sleeping bag is that because it’s spacious in design, you’ll be able to add in additional layers inside the sleeping bag for extra warmth. You can also use the full-length zipper to give yourself extra ventilation during the summer.

Value for Money and Guarantee

If you’re a beginner camper and/or backpacker, you may see the price of this sleeping bag as a little steep. However, for approx. $450, this bag is actually a great investment.

WM Megalite with sack

Of course, there are cheaper sleeping bags available that’ll be able to provide you with warmth and comfort, however, they may not include the lightweight feature which many campers and backpackers look for in a sleeping bag.

In addition, this sleeping bag is of high-quality and is extremely durable. It’s been tested over and over again, compared to other high-quality sleeping bags and yet, this one continues to be ranked at the best of the best. So, for what you pay, you’re getting an amazing product.

In terms of guarantee, all products of Western Mountaineering are protected under a limited lifetime warranty. So, if you have any manufacturer’s defects, they will either repair or replace your sleeping bag free of charge.

Unique Features

The Megalite Mummy isn’t a sleeping bag that’s going to offer you a tremendous amount of additional features. Instead, they’re going to focus on making the essential features outstanding. So, when it comes to unique features, we’re going to have to talk about the weight.

WM MegaLite unique features

The Megalite Mummy’s biggest and best feature is the fact that it’s extremely lightweight. You want a sleeping bag that will easily clip onto your backpack and won’t weigh you down as if you’re carrying a boulder on your back.

It weighs less than 2 lbs, so you won’t even remember you’re carrying it on you.  Another unique feature is that this sleeping bag, including all Western Mountaineering products, are made in the USA, so you’re investing in a high-quality product.

Close competitors: Other Products

Now, we don’t want to show you just one sleeping bag. Of course, you may have other needs that you feel the Megalite Mummy doesn’t provide you. So, with that being said, we want to show you other sleeping bags that are just as good at the Megalite Mummy, however, may suit your outdoor needs better.

Sea to Summit Spark SP III Sleeping BagSea to Summit Spark SP III Sleeping Bag

The Sea to Summit Spark SP III Sleeping Bag is the warmest bag in the Spark series as it’s a -4 degree Celsius bag. Now, this sleeping bag is extremely lightweight, weighing 1.38 lbs, however, it does give up some of the luxuries in order to obtain that lightweight.

It achieves its lightweight by using 10D UL Nylon exterior fabric that’s treated with DWR, a water-resistant coating. It’s highly compactable and compressible, not as good as the Megalite Mummy, however, it’s not far behind.

Now, if you’re in need of more space in your sleeping bag, then you may find this one to be a little too snug. It’s the tightest bag in this review, so if you’re used to the classic mummy-style sleeping bag, you’ll notice that this bag is even tighter. In the case of space, this bag won’t provide you with that extra room to roll around in. In terms of versatility, you’ll be able to take this sleeping bag with you wherever you go – it’s easy to travel with, it’s lightweight and warm.

It’s ideally a 3-season sleeping bag, so other than winter, you’ll be able to use this bag almost year-round. However, when it comes to car camping, it’s not as comfortable. Basically, this is bag is ideal for someone who is really focused on cutting weight from their bag.

Western Mountaineering Ultralite Sleeping BagWestern Mountaineering Ultralite Sleeping Bag

The Western Mountaineering Ultralite Sleeping Bag is the brother to the Megalite Mummy. It’s a great 3-season backpacking or camping sleeping bag that you could stretch into a 4-season bag. It’s a warmer bag than the Megalite Mummy, however, isn’t as spacious. So, if you’re a larger person, you may find this bag to be on the tighter side.

Without any extra blankets or clothing, you’ll be able to withstand temperatures as low as -6. However, if you bundle up, you can easily hold up against temperatures as low as -10. The bag is built with continuous horizontal baffles that allow you to shift the down around, so you’ll be able to control where the heat goes.

Given its name, you know that this bag is lightweight. It weighs only 1 lb 13 oz, so, it’s lighter than the Megalite, however, it’s not as warm and spacious.

Mountain Hardwear Spark 35 Sleeping BagMountain Hardwear Spark 35 Sleeping Bag

The Mountain Hardwear Spark 35 Sleeping Bag is a great sleeping bag if you’re looking for a bag that’s easy on your budget. Now, it’s affordable in comparison to the Megalite and Ultralite for one reason, it’s synthetic. The other sleeping bags we mentioned above use natural down as insulation, however, with the HyperLamina, it’s made with synthetic fibers.

Synthetic bags do break down faster than down fill, however, for a synthetic bag, it’s actually pretty good. Now, this bag isn’t made for temperatures below 1 degree Celsius, so depending on where you’re camping, you may be able to use it as a 3-season bag, however, most likely, you’ll be only using this for summer and late spring/early fall.

It’s insulated with Thermal Q which is a proprietary insulation that’s designed by Mountain Hardwear. It’s lightweight, weighing 1 lb 12 oz, and highly compressible, however, this also means it has a shorter life span. This sleeping bag is ideal for those who will be camping and/or backpacking in areas which are more prone to moisture.

Generally, most people opt for a down fill sleeping bag, however, this is one of the better synthetic sleeping bags on the market.


Whether you’re an experienced backpacker/camper or it’s your first time out on the open road, you want gear that’ll support you and give you a positive experience on your journey. You don’t need to fill your backpack with a bunch of gadgets; instead, you want to invest in a couple essentials that’ll be your backbone for your trip.

That being said, you need a durable, warm and secure sleeping bag. The Megalite Mummy sleeping bag is one of the lightest sleeping bags on the market, giving you extra interior space for comfort and extra mobility.

Many people complain that their sleeping bags are too heavy, bulky and constricting, however, with the Megalite, they removed all these concerns in their design. The Megalite is lightweight and allows users to easily pack it up and slip it into their backpacks without any hassle.

With its durable exterior fabric, continuous baffle system and compressibility, you decide where you want the heat and how warm you want your sleeping bag to be. It gives you the control that many sleeping bags simply don’t offer.

Now, no product is perfect and we know that. So, we want to show you the advantages and disadvantages of the Megalite Mummy so that you can decide for yourself.


  • Lightweight
  • Great breathability
  • Warm
  • Great shoulder girth
  • Large and cosy interior
  • Small travel size
  • USA made
  • Water resistant


  • Zipper occasionally snags

For a down filled sleeping bag, the Western Mountaineering Megalite Mummy sleeping bag is an exceptional bag that’ll protect from any harsh weather and keep you safe and warm. Though this bag doesn’t come with any extra features, Western Mountaineering focused on the essentials, thus, by keeping the design minimalistic, they created a bag that is both lightweight and cosy.

Western Mountaineering Megalite Mummy Sleeping Bag
  • Packaging
  • Design and Durability
  • Comfort
  • Weight
  • Versatility
  • Value for Money and Guarantee
  • Unique Features


One of the lightest sleeping bags on the market, the Megalite Mummy blends both comfort and transportability in one. Weighing less than 2 lbs, this sleeping bag one of the lightest on the market.Whether you’re on the smaller or larger side, this sleeping will provide you with enough interior space for you to comfortably sleep on your side or stomach. The Megalite Mummy will be able to keep you warm during temperatures as low as -1.2 degrees Celsius. So, if you’re planning on traveling with this during the winter, you may need a more winter-appropriate bag. However, for late spring, summer and early fall, this bag is great.

If you’re looking for flaws, there are hardly any in this sleeping bag. Western Mountaineering focused on understanding what backpackers and campers really need in a sleeping bag, thus, they created this one. So, any issues that you had with your old sleeping bag, you won’t be seeing it in this one.

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Western Mountaineering Megalite Mummy Sleeping Bag: Sleeping in the CloudsHave you used this sleeping bag before? If so, let us know what you think about it in the comments below!


Mark Foster

Mark Foster

Mark Foster loves to push his limits when it comes to survival in the wilderness. He might go for a 30-days adventure without any food or equipment except for a survival kit and a knife. We should mention that his survival kit has 122 items in it, so he know what he is doing. Mark is working on his book to share with the world all his experience gained during those brave adventures.