Tailfin Rear Top Tube Bag review

Tailfin continues to expand its range of bikepacking bags, with the latest addition being a rear top-tube bag designed to maximise easy-access storage on the move. Offering a secure fit and an impressively smooth zip, it’s a pack that proves exceptionally user-friendly while riding.

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Tailfin Rear Top Tube Bag – Technical Details

The addition of a rear-specific top tube bag from Tailfin comes as little surprise, especially given that many of the brand’s sponsored athletes have been using alternative solutions to maximise available space on their bikes. While some riders have opted for a downtube pack and others have made use of the original front top tube bag, Tailfin has clearly listened to feedback and developed a purpose-built design that addresses the specific challenges of rear top-tube fitment.

Tailfin Rear Top Tube Bag comparison.jpg, by Matthew Page

The bag is offered in two sizes. The first, with a 0.9-litre capacity, is tailored to road and gravel bikes. It features a narrower profile and a 100-degree mounting angle suited to typical top tube/seat tube junctions. The second, aimed at mountain bikes, has a slightly reduced capacity of 0.8 litres but a broader footprint and lower height, allowing better compatibility with dropper posts. Both versions share a tapered profile—wider at the base and narrower at the top—to reduce the chances of knee or thigh rub while pedalling.

Tailfin Rear Top Tube Bag sizes.jpg, by Matthew Page

Construction is consistent with what we’ve come to expect from Tailfin, using familiar materials such as 210D Hypalon and 210D Diamond Ripstop. The zip runs front to rear and features a generous garage with an integrated gutter system designed to channel away pooled water—an especially useful detail in wet conditions.

Mounting is handled by Tailfin’s V-Mount system on the base, which has three available slots to choose from, complemented by an optional rear strap, with one longer section for the MTB bag, and two locations for the taller road/gravel bag. Three straps are supplied, but Tailfin notes that only two may be needed, depending on the bag’s contents.

If you’re already running a Tailfin frame bag, the V-Mounts can be shared, simplifying setup. The optional rear strap also enables compatibility with bikes running dropper posts that have minimal clearance near the seat clamp, which is a valuable detail for smaller riders or those maximising post insertion. For the 0.8L version, Tailfin recommends at least 150mm of clearance to avoid saddle interference when dropping the post.

Tailfin Rear Top Tube Bag Strap.jpg, by Matthew Page

Inside, carbon fibre baffles help maintain the bag’s shape and prevent bulging, while also adding just enough structure to allow one-handed opening and closing. Another neat touch, also found on the front Top Tube Bag, is the removable padded insole, which makes it ideal for quick and easy cleaning.

Tailfin Rear Top Tube Bag Open.jpg, by Matthew Page

The claimed weights are accurate. Our bags weigh 88g for the road/gravel version, 91g for the MTB, and the straps weigh 12g for the longer 18.5cm and 10g for the 14.5g. That gives a weight range between 108g and 125g, depending on the combination chosen.

Tailfin Rear Top Tube Bag – Performance

During testing, I had access to both bag sizes and fitted them to a range of bikes to assess compatibility and usability. Tailfin provides a downloadable PDF fit guide on its website, which helps determine the best option for your bike. In practice, I found the sizing intuitive: the narrower road/gravel version fitted my Lauf Seigla perfectly, while the wider MTB version was well-suited to the Trek Supercaliber.

Tailfin Rear Top Tube Bag Zip.jpg, by Matthew Page

Each bag comes with three straps: two longer 18.5cm straps and one shorter 14.5cm version. For most setups, this will be more than sufficient. However, on the Trek Supercaliber, I needed to use longer straps than Tailfin provides due to the position of the rear shock. This is a niche case and unlikely to affect most users.

The zip is impressively smooth and easy to operate, whether the bag is full or empty. The internal baffles do a great job of maintaining the bag’s shape, preventing the fabric from folding. I had initial concerns about the zip garage collecting water, especially with the front-to-rear zip orientation directing rain towards it. However, the gutter system works exactly as intended, with a small drainage hole at the base that effectively channels water away.

The zip begins low on the bag, making the most of the internal space and simplifying access. Storage space proved ideal for stashing food, tools or a spare tube. One small cautionary note: the full-length zip and the bag’s rearward position on the bike mean that if you forget to close it, it’s much easier for items to fall out—especially on descents—than with a front-mounted top tube bag. It’s not a flaw in the design, just something to be mindful of. Lesson learned the hard way.

Tailfin Rear Top Tube Bag Open.jpg, by Matthew Page

On the trail, the tapered shape kept the bag almost unnoticeable while pedalling. Despite a naturally narrow pedalling stance, I experienced no knee rub and barely any contact with the bag at all during rides while riding in or out of the saddle.

Tailfin Rear Top Tube Bag – Verdict

There are only a few rear-specific top tube bags available. The closest competitor is Apidura’s alternative, which costs the same, uses similar materials, and offers one litre of space, though its zip opens in the opposite direction. Restrap also offers a more affordable option at £38, but its lighter materials feel flimsy, the zip is harder to use, and it doesn’t offer the same level of weather protection.

Tailfin has a reputation for releasing products only when they’re confident in the design, and that approach is clear here. While this is a relatively simple product, it’s been carefully thought through and executed to a high standard. It solves key problems without introducing new ones—and that’s what makes it stand out.

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