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The Pipedream 600 from Alpkit is a goose down sleeping bag designed for winter cold, with a high (750 FP) fill and a water-repellent coating. It packs down small enough to fit into many bikepacking saddle bags, but this level of spec comes at a price.

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With sleeping bags the old mantra – you get what you pay for – is very true. If you want a bag to keep warm in full British winter that's small enough to pack up into typical bikepacking bags, that is almost certainly going to mean down for insulation. And quite a bit of it, too.

The PipeDream range of sleeping bags have a 750 FP (fill power) rating, with the number refering to how lofty the down is and how much air will be trapped inside. The higher the number, the warmer it is. Then there is the fill weight, which is where the 600 gets its name – it takes 600g of down.

The construction of the mummy-shaped bag is reasonably simple, which helps keep the overall weight reasonable. There are horizontal baffles which are filled independently to ensure the down stays evenly spread.

The bag has a reasonably slim leg area designed to help with warmth, and I was genuinely surprised how well it works – cold feet is something I've really struggled with I the past.

The PipeDream is limited to just two sizes, plus the option of which side the zip is on. The regular has an internal length of 190cm, and the large is 210cm. Both are 75cm wide.

There is no half-zip option, although this is unlikely to be used as a lightweight competition-style bag, so it's perhaps not surprising.

Packed in compression size. 750ml bottle for comparison

The huge benefit of down over synthetic is the warmth to weight/space ratio, and while synthetic insulation is improving, you're still looking at around double the weight. Down's packability is also good: I managed to get this into a 10 litre saddlebag and even (though only just) a 4.5L Miss Grape fork bag (see pic below).

Squeezed into the compression sack provided, the bag measures approximately 30x20cm with a circumference of 65cm, but it is possible to pack it into a smaller space still.

The down is ethically-sourced, RDS standard goose, which means the birds are not live plucked, force fed or mistreated. The down is also treated with a durable water repellent coating which is PFC free and non-toxic.

Through testing I had times when the bag got damp, but at no time did the down collapse, which gives me confidence the DWR works well.

I used the PipeDream 600 through a range of autumn and winter temperatures, and every time it impressed. (For context, I would not consider myself an especially warm or cold sleeper, with perhaps the exception of my toes.)

Double zip helps regulate temperature

Up to 7 degrees I found this absolutely fine – comfortable, with a good level of breathability, and never hot and sweaty.

The lower limit is likely a bigger concern for many, and the 600 has a comfort limit of -12°C. The lowest I experienced during the test was -4°C however, at which level it was simply brilliant – it gave me a very comfortable, uninterrupted night's sleep with no cold spots. Even my feet stayed warm.

One feature I really like is the neck baffle with its sculpted shape that really falls into place to keep drafts out. While it might seem basic compared to some designs with a cord adjustment, I found it far easier with no searching for the cord when trying to get out.

The head area does have a cord closure, but this is in an area that's easier to find.

Zip baffle helps ensure it stays warm

If the PipeDream 600 sounds too warm, Alpkit does  the PipeDream 200 and 400 versions for hotter weather.

At £270 this isn't cheap, but you'll struggle to find a bag that can cope with genuine winter temperatures for much less. Rab's Ascent 900, for instance, has a similar Comfort Limit (EN13537 scale) but it's £290 and weighs 500g more. 

British company PHD makes some of the most well-regarded down items with incredibly low weights for the warmth, but an equivalent bag from them – the 790g Hispar 400 – is £657.

Cotton lofting bag also provided for storage

The Alpkit PipeDream 600 impresses with an exceptional performance, reasonably low weight and a usefully small pack size. It's good value compared to the competition, too, even before Alpkit adds any discount – at the time of writing it was available with a good chunk off at £230.

• alpkit.com

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