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Review: Big Agnes Women’s Sidney SL 25 Sleeping Bag

Woman in bBig Agnes Sidney sleeping bag

A customisable, responsibly sourced, water repellent down sleeping bag with some superb added extras for warm cosy sleeps in the backcountry like never before.

The innovative design of the Big Agnes Women’s Sidney SL 25 sleeping bag is in a league of its own. It has an REM Pad Sleeve to keep you from rolling off your pad, 650 fill power DownTek to preserve its insulation when wet and an insanely cosy hood design. And to top it off, the Sidney is complete with a customisable cinch system to alter the fit of your sleeping bag to suit the conditions – sleeping bag innovation at it’s very best. This is an ideal sleeping system for backpacking and trekking as well as car camping, and everything in between.

Big Agnes Sidney SL 25 sleeping bag: The stats

Comfort rating:25ºF (-4ºC)
Insulation type:650 fill down
Weight:2.2lbs (992g)
Length:70in (178cm)
Stuff sack size:7.5 x 15in (19 x 38cm)
Shell material:Ripstop nylon with water repellent coating

Design features of the Big Agnes Sidney SL 25 sleeping bag


Sleeping bag insulationThe Sidney is filled with 650 fill power duck and goose down that is sourced from a Responsible Down Standard (RDS) Certified supplier. An essential requirement for me. It’s not just the happy flappers that make this down extra special: Big Agnes use DownTek – down that is treated with a DWR to minimise the negative effects of water on the insulation. Pretty great!

To maximise on this super techy water repelling down, the Sidney features vertical side walls where contoured baffles help to trap heat closer to the body, and a baffled draft excluder to stop the breeze from getting through the full length zipper.


Hood tie of sleeping bagTogether with a big internal anti-draft collar that prevents outside air sneaking down into the bag, the hood is also contoured to the shape of your head making it super warm and cosy. The single low profile cord lock on the side of the hood lets you un-cinch the hood using only one hand, and has a short cord that doesn’t get in the way. To finish off the cocoon-like cosiness of the Sidney hood is a really nice touch that prevents the cold, hard zipper pull from rubbing your chin whilst you sleep: an internal zipper garage! Pull the zipper tie to the inside of your bag and tuck it into its garage to sleep for the night. It’ll be right where you left it when it’s time to unzip – from the inside!

REM pad sleeve

Sleeping bag sleeve clipsThis is a really nice added extra to the sleeping bag. When you’re not out getting cosy in your Sidney the REM is put to work as a storage sack to prevent the down from being compressed in its stuff sack. But out at camp it transforms into a pad sleeve that links to the sleeping bag keeping it securely on your pad. Put the head end of your sleeping pad into the sleeve and attach the 6 hooks on the backside of the Sidney into the clips on the sleeve. This system keeps you from rolling off the pad, and also prevents your sleeping bag from getting twisted and confused during the night (this only really applies to nighttime wrigglers and turners!).

Exterior cinch system

Sleeping bag cinched downTo help trap more heat closer to your body, Big Agnes have developed this innovative system that provides the warmth you need according to the conditions and your own sleeping temperature preferences. There are 3 clips on each side of the bag between the hips and the toes, and 2 clips on the bottom of the bag to cinch down the footbox. Using this system can take a bit of getting used to if you are used to having loads of room to wriggle in your bag. But keep trying different combos of clips to figure out what feels the best and most warm for you.

Interior features

Internal pocket of sleeping bagThe inside of the Sidney is lined with Nylon Taffeta for a very cosy and soft finish. There are 4 loops inside the bag (2 at the bottom and 2 at the top near your shoulders), to attach a sleeping bag liner to should you choose to use one. And there’s also a handy and low profile zippered pocket inside the bag at around chest height. Good for storing a tissue in, or your mini teddy?!

The foot of the sleeping bag

Sleeping bag footboxThe vaulted shaped of the footbox means that there is more space to move your feet around and no compression from tightness causing cold spots. This can of course be cinched down to eliminate dead air if you find that your feet don’t reach the bottom of the bag. Another nice feature are the 2 external loops at the foot of the bag to hang it up for storing, airing or drying.

Big Agnes Sidney SL 25 sleeping bag review

This Sidney SL 25 sleeping bag makes me a very happy lady! And although it’s not the lightest, warmest or smallest sleeping bag in the world, the exceptionally well thought through design makes it the ideal sleeping bag for all of my outdoor adventures. There are very few scenarios where I would choose to camp in conditions much below zero (32ºF), but for those rare times I love that I don’t need a whole other sleeping bag! At 2.2lbs (992g) the Sidney is just light enough for backpacking and trekking, without having to compromise on warmth. This is a HUGE bonus for me as I am a really cold sleeper (and person!). In the past I’ve always chosen warmth over weight. But this little beauty means that I no longer have to lug a 3lb sleeping bag around with me to stay warm at night.

The ability to cinch down the sides of the sleeping bag is what makes the Sidney such a versatile bag and so well suited for use in wide range of temperatures. I didn’t get on with this system to start with and found it a little restricting. But having persevered, I’m converted. I’ve found that once I’m asleep I don’t notice that I’m in, what is essentially, a smaller sleeping bag.

REM pad sleeve

The REM Pad Sleeve is also another great feature that took me a few sleeps to fully realise its benefits. When in my small backpacking tent with another person, who is also on a sleeping pad, there is zero chance of me falling off my pad as there is simply no room. However, I’ve recently slept out a few times without a tent – this is where the REM sleeve comes into its own, especially when the ground isn’t as even as one might prefer! It keeps you where you should be. Forward thinking from Big Agnes, as sleeping pads only seem to be getting fatter and fatter!

I also find that connecting the sleeping bag to my pad means that when I toss and turn a lot in my sleep, my bag stays put and I don’t end up with the opening of the hood facing down.

What I love the most about the Big Agnes Sidney SL 25 sleeping bag

The hood is awesome. The opening to the sleeping bag is face-sized, which may sound like an obvious requirement, but I have used other sleeping bags where you have to really pull in the drawstring to get the opening to the right size. I like this because it means I am instantly cocooned in the bag, with no faffing with strings to tighten the gap. When it’s super cold, and I only want my nose poking out for air, the cord lock is short and easy to adjust with only one hand. No long and complex cords flapping around my face to get my hands tangled in when I try to adjust them!

The shape of the hood is also perfect. Big Agnes have really thought about eliminating all the unnecessary air pockets in the SL 25, and the ‘head-shaped’ hood is an excellent example of this. The contoured baffles create a cosy nest for your head that feels much like the hood of a very plush down jacket. Together with the oversized anti-draft collar, the whole hood design rocks my wild snoozing world!

Sleeping bag

What I don’t love so much about the Big Agnes Sidney SL 25 sleeping bag

There is little to dislike about this all round excellent bag. The one small thing I have noticed, however, is that the clips that connect the REM bag to the loops on the sleeping bag have a very narrow opening. You really have to take your time to carefully post the flat loops on the side of the sleeping bag into the clips. They are super easy to unclip, and are secure once they’re in. But getting them in can be kind of fiddly (especially when you have cold hands and bad light!). I’m assuming that the idea behind this is to keep the clips as flat and low profiled as possible so that you won’t feel them should you roll onto them in your sleep.

I’ve been using the bag now for 3 years and in the last year I’ve started to have problems with the down clumping up inside the baffles, causing cold spots. The down is then difficult to shift back into place. I’m hoping that a Nikwax down treatment will revitalise and re-puff the down.


The Big Agnes Women’s Sidney SL 25 sleeping bag is one versatile sleeping bag that will see you through many happy and cosy nights out on the trail, car camping, or travelling. The Sidney is light enough to hike with without compromising on warmth, and has some exceptional innovations and features to make this an all round excellent choice for women wanting to sleep easy in their element. I can’t wait to use mine again!

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Disclaimer: Cool of the Wild received this product free in return for an honest review. We only recommend gear that we love from companies we trust and we are under no obligation to give a positive review. All thoughts and opinions are that of the reviewer and we are in no way influenced by the brand or company.

About Joey

Woman wearing wooly hat

Joey is based in Cornwall, UK, and runs Cool of the Wild. She can’t get enough of being outdoors – whether that’s lounging around the campfire cooking up a feast, hitting the trail in her running shoes, or attempting to conquer the waves on her surfboard – she lives for it. Camping is what she loves to do the most, but has also spent many hours clinging to the side of a rock face, cycling about the place, cruising the ski-slopes on her snowboard, and hiking small mountains and big hills.

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