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Ultra light, ultra warm and ultra packable, the Spark SPIII is perfect for those who require a high performance sleeping bag without the overwhelming weight and large pack size. 
Ultra light, ultra warm and ultra packable, the Spark SPIII is perfect for those who require a high performance sleeping bag without the overwhelming weight and large pack size. 
Sea to Summit

Sea to Summit Spark SpIII Long Sleeping Bag

£423.00  £470.00  10% off
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Estimated Delivery & Collection Dates

Estimated Delivery & Collection Dates are given on Pre-Order and Pre-Launch products. They are for indication purposes only and can change at any time without notice.

The dates we provide are based on indications given by our suppliers. Whenever we get updated information from our suppliers we will endeavour to update the Estimated Delivery & Collection Dates provided on product pages.

We estimate this will be ready for despatch to you or collection via Click & Collect on the Undetermined

Sea to Summit Spark SpIII Long Sleeping Bag Information

Season : 2020W R

Brand : Sea to Summit

Code : ASP3-L-3 Long

What is the Spark SPIII?

The Spark is one of the lightest, most packable sleeping bags available relative to the warmth it provides, weighing an incredible 745g. If you've been searching for a sleeping bag that provides high amounts of warmth without the excessive weight and pack size, the Spark should be at the top of your list.

What is it made of?

Insulation: The key to the Spark's unbelievable pack size is the super lightweight outer fabric and high quality insulation. Starting with the insulation, Sea to Summit fill the Spark with 430g of 850 fill-power, UTRA-DRY treated, RDS certified Premium Goose Down. We know that's a lot of jargon, so let's break it down. 850 fill-power down is some of the highest quality insulation available and allows the bag to pack down to a miniscule size yet provides an exceptionally high amount of warmth relative to its weight. ULTRA-DRY treated down vastly improves the down's reaction to water without affecting its weight or warmth. Essentially, it will retain 60% more loft and absorbs 30% less moisture than untreated down. RDS certified down ensures that the feathers used in the sleeping bag come from animals which have not been subjected to unnecessary harm. To sum all of that up, it performs better in damp conditions, uses some of the highest quality down available and sources it in an ethical and sustainable manner. 

Outer fabric: Further contributing to the astonoshing weight of the Spark is its 10D nylon outer fabric. This outer fabric is by far one of the most packable, lightweight fabrics we've seen on a sleeping bag; it's so lightweight that you can actually see the down through it! Inside the bag lives an even thinner 7D nylon, allowing the Spark to pack down to the same size as two 500ml water bottles placed side by side.

What is the construction used in the sleeping bag?

It isn't just a series of space-age materials which make this bag so light and packable, it also comes down to where the insulation is placed. You'll notice in the picture above that some baffles are positioned vertically and some horizontally; this isn't just to make it look cool, they do serve a purpose! Vertical baffles on the chest area prevent the down migrating and creating a cold spot, while large horizonal baffles on the lower add warmth to your torso. All of the down is stored in these baffles in a box wall construction, increasing warmth even further and reducing the chance of heat escaping. Each baffle is also contoured to give the sleeping bag its 'mummy' shape, reducing the amount of dead space inside and decreasing the overall pack size.

What are the features?

Features wise, you get a full side zip with two sliders to allow you to ventilate if needs be, a zipper draft tube to prevent heat escaping through the zip, another draft tube on the neck and collar to trap warmth more efficiently and lastly a Sea to Summit logo on the yellow baffle next to the zip. The features are kept to a minimum to prioritise pack size and weight. 

How does it fit?

Unlike the SpI which features a pretty snug fit, the SpIII is cut larger to allow you to wear thick clothing without feeling restricted. The mummy shape still hugs you nicely and is incredibly efficient, but you do have a little more wiggle room. This particular variant is the 'long' version, meaning a longer length for those over 6ft. 


We know this bag won't be for everybody, but for those demanding the lightest, most packable sleeping bag available for autumn/winter persuits, look no further. 

  • 10D outer fabric
  • 850+ fill-power down
  • Hydrophobically treated
  • Full length zip
  • Ultra small pack size
  • Large glove friendly zip
  • Long length

How warm a sleeping bag do you really need? We’ve tried to help you by grouping our sleeping bags by their recognised comfort ratings. These are the ratings supplied by the brands that indicate the temperature at which you will remain comfortable whilst sleeping on a good insulated sleep mat. After all, comfortable is what you want to be when it’s cold and wet outside and you’re all tucked up in your nice warm sleeping bag.

We always recommend that you choose your bag according to the coldest conditions you will experience; you can always unzip a bag if it is too warm, but trying to sleep when you’re too cold is just miserable. Bear in mind that that we are all individuals and we all feel the cold differently, and that our own resistance will fluctuate depending a whole load of factors including how much we have eaten, whether we have consumed alcohol, whether we need a wee or what kind of mood we are in!

Sleeping bags do not generate heat they only trap the heat we produce so it is vital that you get into your bag when you are giving off warmth, don’t go to bed when you are cold, have a hot meal or a hot drink or do some brisk exercise to get you nicely warmed up.

Traditionally sleeping bag manufacturers provided their own temperature ratings based on their experience, the products intended end use and the perceived environment. But each brand tested their bags in different ways and it was hard to find a fair comparison between models. So, in 2005 a European standard for sleeping bag temperature ratings, EN 13537, was introduced to give consumers a comparable guide to sleeping bag performance across a range of brands and models. The ratings have four different temperature ratings to give you an indication of the bags performance.

Upper limit: This is the highest temperature at which an average male should experience a comfortable night’s sleep.

Comfort: This is the temperature at which an average female should experience a comfortable night’s sleep. On average women sleep colder than men so this rating is some degrees above the ‘comfort lower limit’ for a man.

Comfort lower limit:  This is the lowest temperature at which an average male should experience a comfortable night’s sleep whilst lying in a curled-up body position. This used to be known as the comfort rating.

Extreme: This is a survival rating where the user is likely to suffer health damage such as Hypothermia. It should be treated with the utmost caution and not be relied on for general use.

However, the EN 13537 European Standard does not apply to down filled sleeping bags with a fill weight of more than 800g; for those bags you will have to rely on the manufacturer's experience and technical expertise, which is often more accurate!

Most reputable brands still use their own rating system alongside EN 13537, for instance the M.E “Good Night’s Sleep” and Rab’s “Sleep Limit”. These ratings are often the most accurate guide to the overall performance of a bag being used by an average outdoor enthusiast. They are based on years of expedition heritage, field trials, technological experience, and constant feedback.

But please bear in mind that all ratings are only a guide and, as mentioned earlier, there are a huge range of factors that can affect your comfort, if you are just not sure it is always wise to go for a warmer model.

The biggest difference you can make to your overall comfort is to use an efficiently insulated sleeping mat. Once you get inside your sleeping bag you instantly compress all the filling beneath you, greatly reducing its efficiency. The use of a quality sleep mat will ensure you are properly insulated from the cold ground and you will of course be a lot more comfortable. Your sleeping bag is only as good as the mat that’s beneath it; we recommend EXPED, ThermaRest or Multimat sleeping mats for comfort and insulation.

Technical Information

Insulation: 850 Fill-Power RDS Certified, ULTRA-DRY Goose Down

Outer fabric: 10D Nylon

Inner Fabric: 7D Nylon

Fill weight: 485g

Overall weight: 745g

Comfort rating: -2°C

Lower rating: -8°C

Sizing Information
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