• Weight (regular) 890 grams
  • Recommended Maximum User Height 170 cm
  • Female Comfort Rating -10
  • Male Comfort Rating -17
  • Cost $949.00

Sea to Summit Flame FMIV Women’s Sleeping Bag Regular

Sleep Systems-Women


Rating: 8.9 / 10
Weight 1.9 / 2
Value for Money 1.7 / 2
Durability 1.7 / 2
Warmth 1.9 / 2
Versatility 1.7 / 2

Sea to Summit Flame FMIV Women's Sleeping Bag Regular Review

I have been thinking about a new sleeping bag for a while now. My Mont Brindabella Hyrdonaute XT sleeping bag is great but it’s bulky, heavy and no longer available. Tim wasn’t in any enamoured with my Mont and complained heavily every time I took it out of the compression sack because it instantly filled every space corner of our tiny tent!

I am a complicated cold sleeper. When I head to bed I am freezing and shiver until I warm up. Then I get too warm and need to cool a little so being able to ‘escape’ from my sleeping bag is important. I thought my search was done when I tested the Sea to Summit Flame FMIII Women’s Sleeping Bag but continued to procrastinate and then the Flame FMIV appears on the market and I am hooked!

Sea to Summit is one of a growing number of companies that use ‘ethical down’ which is a polite way of saying they don’t pluck down off living birds. This does increase the cost but is clearly a more a humane way of collecting the down. The down is also hydrophobic which means it repels water so if it gets wet, it will still keep you warm. The Flame FMIV Women’s bag is filled with 850+ loft goose down and will keep you warm down to an amazing -10° Celcius. I’ve tested this bag in cold weather, not near -10 (yet!) and I was at a comfortable temperature almost immediately.

The regular-sized bag suits me well. I’m average height and found there was plenty of room. If you are taller than 170 cm then the long version is best for you. The shape is ‘mummy’ style and contoured to the female body which means that it tappers in the leg area and down to the feet. This reduces the amount of air in the bag that you need to heat. I’m not usually a fan of the mummy-style sleeping bags given I tend to feel a little too constricted but I don’t feel that with the Flame IV.

The Flame FMIV is the twin to the Spark series which is classed as unisex but tends to be sold to males. The main difference between the two is a difference in length and width with the Flame series being slightly wider in the hip area, narrower at the chest and having an extra degree of warmth aimed for women who from a physiological perspective, tend to feel the cold more than men. However, I’d ignore the gender descriptions on these bags and choose the model that best fits your personal dimensions and cold tolerance. If you are a male, then this bag will take you down to and impressive -17° Celcius.

The Flame FMIV is dark grey in colour with a deep orange inner. Sea to Summit has cleverly coloured its bags – the darker the outer layer, the warmer the bag. Such great thinking and very easy to navigate the range when you’re tying to work out the best one for you. Some of Sea Summit’s lighter weight bags have a very pale inner lining which could get dirty easily. I use a Sea to Summit bag liner to keep my sleeping bag cleaner for longer.

As an ultralight bag, the outer and inner shell use very lightweight materials (7 Denier Nylon shell and lining fabric) so if you are really rough with your gear then there is potential for you to tear the bag. This is not a bag to loan to a novice hiker friend or use as a hire bag!

The Flame FMIV is a high-end bag. It has draft tubes at the front and back of the neck as well as along the zip to minimise airflow. It has a 3/4 length 2-way zip. This means the toe box can’t be flattened out to form a quilt like other heavier grade bags. The other thing missing is an internal security pocket for a wallet or phone – this doesn’t worry me too much.

Sea to Summit includes a design feature on all its higher-end bags – horizontal down baffles on the upper body and vertical down baffles on the lower body. This means the correct amount of down is kept in the right area of the bag to keep you warm. The hood on the Flame FMIV fits close – a result of the weight savings during the design process. I’m used to a more generous hood but the smaller size on the Flame didn’t concern me as much as I thought it may.

The Flame FMIII packs down to a very tiny size and weighs 890 grams for the regular size – a little heavy but lighter than most bags with this warmth range. Given sleeping bags are often one of the heaviest and bulky items you will carry in your pack, this bag is a real weight and space saver given it packs down to about 2/3 he size of my previous bag.

I really like this sleeping bag but there is one negative, for many the biggest, and that is the cost. With an RRP of AUD$949 for the regular size, this is an expensive bag. You can find it on sale for around AUD$790 but that’s still a decent investment.

This is a great bag if you are looking for a super warm, lightweight sleeping bag. Gill loved this bag so much that this is what she ended up purchasing.

We Like

  • Women’s specific contoured mummy shape that minimises airflow to keep you super warm 
  • 850+ Loft ULTRA-DRY Down provides great insulation and keeps the packed size very small
  • A combination of vertical chest baffles and horizontal lower body baffles that keep the down in the right places to prevent cold spots
  • 3/4 side zip with two sliders provides easy access and extra ventilation options
  • Zipper draft tube, and hood and front neck draft collar prevent warmth being lost

We Don't Like

  • The price! This is a high warmth technical sleeping bag that isn’t cheap so if you only camp for a few nights of the year it will be hard to justify.
  • Handle with care as the outer and inner shell are made from lightweight materials and potentially fragile if you are too rough
  • The drawstring toggle on the neck is a bit small for people with bigger hands. A slightly larger toggle would improve the ease of use particularly on those cold nights when your hands aren’t working so well
  • Not really a year-round bag, best for cool to very cold conditions
  • No foot box zip which limits the versatility of the bag

Best Uses

  • The perfect bag for hikers who want a super warm bag that doesn’t weigh a ton

Buy One

You can purchase the Sea to Summit Flame FMIV Women’s Sleeping Bag Regular from Snowys, Wild Earth, or from Wildfire Sports

Disclosure:  We may earn a small commission, at no additional expense to you, if you click through and make a purchase. Please note that our affiliations do not influence, in any way, the independence of our reviews. If we don’t like a product, you’ll hear about it from us!


AUD$949 RRP. Keep an eye out for the sales and you may get a great deal on this excellent bag

Sea to Summit Flame FMIV Women’s Sleeping Bag Regular

Flame IV in storage sack

Flame IV in stuff sack next to a 1 litre water bottle

Sea to Summit Flame FMIV Women’s Sleeping Bag Regular temperature ratings. This bag will suit the ‘average female’ down to -10° and the ‘average male’ down to -17° Celcius

Sea to Summit Flame IV size comparisons

Inside view of the Flame IV. The inner shell isn’t as see-through as the Sea to Summit Spark Range

Hood and neck baffles

Gill inside the Sea to Summit Flame FMIV Women’s Sleeping Bag Regular

Clip at the top of the zip

Flame IV hood closed up

Flame IV two way zip

Bag test Certificate


This review was done with product purchased by Australian Hiker

Last Updated

21 April 2024

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