CROSSO Zipper Cosinus Frame Bag

Custom Bikepacking Frame Bag

The Crosso Zipper Cosinus Frame Bag is a custom-made bikepacking frame bag, designed to make the most of the space inside the bike’s main triangle.

Unlike universal frame bags, the Cosinus is made to measure for your frame geometry, eliminating the empty spaces typical of standard bags and using every available millimeter to carry your gear.

The result is a bag that integrates perfectly with the bike, remains stable even on rough terrain, and offers high carrying capacity without compromising pedaling.

Within a bikepacking load system, the frame bag is the ideal place to carry heavier items while keeping the center of gravity low. If you want to learn more about how to distribute weight correctly between a saddle bag, frame bag, and top tube bag, you can also consult the guide Touring and bikepacking bags — guide to choosing, where you will find a section dedicated to load distribution in bikepacking.

Why choose a custom bikepacking frame bag

Every frame has different geometry: angles, oversized tubes, bottle cage space, or cable routing often make it difficult to find a bag that really uses the whole triangle.

The Zipper Cosinus was created precisely to solve this problem.

A standard bag inevitably leaves unused space; a custom-made bag, on the other hand, fills the frame triangle perfectly, increasing carrying capacity and improving the bike’s visual integration.

The main advantage is therefore twofold:

A custom frame bag at a surprisingly accessible price

Custom frame bags are often expensive products because they require personalized manufacturing. With the Zipper Cosinus, however, Crosso offers a tailor-made solution at €123, making access to a frame bag built to the dimensions of your own frame much more affordable than many alternatives currently on the market.

Dual-chamber design: organization and stability

One of the most interesting elements of the Cosinus is its two-compartment internal system.

Inside the bag there is a horizontal divider positioned at about two-thirds of the height, which splits the volume into two chambers.

This element performs two important functions.

Load organization

Shape control

The divider also acts as a sort of structural reinforcement, preventing the bag from bulging sideways when it is very full. This avoids the typical “belly” effect that can cause your knees to rub against the bag while pedaling.

The divider is attached with Velcro and can be:

This solution makes it possible to insert long items such as tent poles, temporarily turning the bag into a single vertical compartment.

Stable mounting with continuous loop system

The Zipper Cosinus uses an adjustable Velcro mounting system, designed to adapt to the specific geometry of each frame.

The edge of the bag features a continuous loop system (daisy chain) that allows the straps to be positioned exactly where they are most convenient.

The set includes eight mounting straps, internally lined with anti-slip material that improves stability and protects the frame paint.

This system makes it possible to:

Materials: abrasion-resistant Cordura® TPU

The Cosinus is made from Cordura® TPU, a material particularly appreciated in bikepacking for its combination of strength and flexibility.

Main features

The closure uses a splash-proof zip, designed to limit water ingress during light or moderate rain.

The bag is made with a stitched construction rather than a welded one: this means the fabric is waterproof but the seams are not sealed. The Cosinus protects your equipment well from humidity and moderate rain, but it is not designed for immersion or very intense, prolonged rainfall.

For water-sensitive items, it is always advisable to use a small internal dry bag.

Pockets and quick access

The Zipper Cosinus includes several details that are very useful during travel.

Inner pocket

Positioned under the main zip, ideal for:

Outer mesh pocket

Located on the side opposite the drivetrain, it is perfect for items you need to use quickly while riding:

How the custom-made order works

Ordering the Zipper Cosinus is simple.

There is no need to enter your frame measurements during checkout.

1️⃣ Place the order

Complete the purchase normally and indicate the desired color in the order notes:

2️⃣ Receive the measurement guide

After the order, you will receive an email with step-by-step instructions for taking the frame dimensions correctly.

We will guide you through collecting the measurements needed to make the bag to size.

3️⃣ Custom production

The bag will be produced specifically for your frame with a dimensional tolerance of ±3%.

As this is a customized product, returns are not possible: it is therefore important to take the measurements carefully.

Frame protection advice

Even though the mounting straps are lined with anti-slip material, vibrations and dust during use can dull the frame paint over time.

For this reason, it is always advisable to apply frame protection tape at the contact points between the bag and the bike.

It is a simple precaution that many bikepackers use to preserve their bike’s paint over the long term.

Integration into the bikepacking setup

Within a complete bikepacking setup, the Cosinus works together with other bags to distribute the load in a balanced way.

Typical configuration

This configuration keeps the weight close to the center of the bike, improving stability and control on long road and gravel trips.

Technical specifications

Frequently asked questions about the custom Crosso Zipper Cosinus frame bag