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BTwin Comp 0.4L Seat Post Bike Bag



Perfect inexpensive small saddlebag

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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This BTwin seat pack is great. Simple and swappable and just the right size for the things you'd normally put in it. I wholeheartedly recommend it.

At a penny under eight quid you're probably not expecting the earth, but the Comp 0.4l Seat Post Bike Bag (another snappy name, chaps) has everything you need. It's a semi-rigid construction with a good quality zip that goes all the way round. There are reflective patches on all sides, and a light loop too. Inside there's enough space for a tube, levers, a tool and a puncture kit.

The best thing about this pack though is the mount. It's sprung, so you just push the two halves in, slip it between the rails and let go. It's stayed put on every ride on a range of bikes, and it doesn't catch my thighs. And if it doesn't catch mine, yours are probably safe.

Taking it off takes about one second, so switching it between bikes is the simplest thing ever and you can take it off when doing repairs on the side of the road too, which is more of a bonus than you might imagine. The design means it'll fit any round-railed saddle. If you have special needs with regards to your rails, you're out of luck. Otherwise, happy days. The first time I fitted it, I fitted it the wrong way round - the mount is sort of counter-intuitive. Once you've worked that out though, it works perfectly on every saddle I've tried, which is a few.

There's literally nothing not to like about it. The mount (hard plastic) has pulled away from the semi rigid case a little bit, so you can see underneath the middle of it, but the rivets holding the two bits together are still tight as new, and it doesn't look in any danger of failing; it's no different from a bunch of other seatpacks I've used in that regard.

Given that it has a 2-year guarantee the worst case scenario is that you have to buy a new one 2 years down the line, so that's an outlay of £4 a year. For the money, I simply can't find fault with it.

Go and buy one. I would say buy two, but it's so easy to swap that there's just no need.


Perfect small budget saddlebag

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Make and model: BTwin Comp 0.4L Seat Post Bike Bag

Size tested: Black

Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

Capacity: 0.4L.

Ease of use: 1 compartment. Attaches to saddle rail. Reflectors.

Low weight / lightweight: 120 g.

Guarantee : 2 Years

Rate the product for performance:
Rate the product for durability:
Rate the product for weight, if applicable:
Rate the product for value:

Tell us how the product performed overall when used for its designed purpose

Without fault.

Tell us what you particularly liked about the product

Great mount, easy to swap between bikes, just the right size.

Tell us what you particularly disliked about the product


Did you enjoy using the product? Yes.

Would you consider buying the product? Yes.

Would you recommend the product to a friend? Yes.

Rate the product for quality of construction:

Overall rating: 10/10

About the tester

Age: 41  Height: 190cm  Weight: 102kg

I usually ride: whatever I'm testing...  My best bike is: Genesis Equilibrium 853

I've been riding for: 10-20 years  I ride: Every day  I would class myself as: Experienced

I regularly do the following types of riding: commuting, club rides, sportives, general fitness riding, fixed/singlespeed, mtb, Mountain Bike Bog Snorkelling, track


Dave is a founding father of, having previously worked on Cycling Plus and What Mountain Bike magazines back in the day. He also writes about e-bikes for our sister publication ebiketips. He's won three mountain bike bog snorkelling World Championships, and races at the back of the third cats.

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