If the devil is in the details, the zippers on your pack can be the difference between an epic success or catastrophic mess. In this Gear Corner story we examine the ways we choose and integrate zippers in the Mountain Series packs, and answer some technical questions. We’ll also explain how the zippers are made, and clarify the terminology used to describe them.

Why Zippers?

Most people take zippers in our packs for granted. That is to say, we love the simplicity, convenience, and protection zippers provide. And we sure love them when they work.  But we don’t think much about HOW they work, or how durable they need to be for a specific purpose, or how weather resistant, or how easy to pull when the pack is full. But if a zipper fails, it’s the difference between a great day of shooting and a nightmare of missed shots and ruined gear.

In fact, zippers are pretty complex devices. And zipper technology continues to evolve over time, so choosing the right zipper is critical. Let’s take a look at the different kinds of zippers, which ones are suited for f-stop, and how they are made.


The Components of a Zipper

To understand the different kinds of zippers, let’s establish what the various components are called. Then we’ll get into how they fit together.

The Top Stop of a zipper is a fixed piece of plastic or metal that prevents the slider from coming off the top of the zipper.

The Slider Body is the piece that joins or separates the teeth as it slides up and down.

The Pull Tab is the part that is connected to the slider body, and enables you to pull it up and down.

The  Chain ( using Teeth or a Coil) are the interlocking pieces that hold the zipper together.

The Tape is the fabric that the teeth or chain are attached to.

A Bottom Stop prevents the slider from coming off the bottom of the zipper. You’ll find a bottom stop wherever you find a closed-end zipper, meaning the zipper does not come completely apart. Think of a fly on trousers or the zip closure on fashion boots.

For Separating zippers like you’d find on the front closure of a jacket, the bottom of the zipper consists of a Retainer Box, into which you slide an Insertion Pin to secure the opposing sides of a zipper and get it started. When the slider body reaches the bottom of this type of zipper, the insertion pin can slide out through the slider body.

There are also Two-Way Zippers that have two slider bodies attached to the same tape. The ends of these zippers can be open-ended or closed, depending on the purpose. For f-stop, these types of zippers will always be closed-ended on both sides.

Hands on: Working closely with our production partners ensures the quality of all our components
- and makes sure your bag is ready for adventure time and time again.

Teeth vs Coil vs Track Type

The main difference between different kinds of zippers is in the “teeth”. Traditionally, zippers were constructed of hundreds of tiny metal teeth, spaced apart just enough to let them interlock when pressed together via a slider. Those teeth are clamped or glued to a cloth tape, which is then sewn to the textile of a jacket or a pack. Eventually the metal components began to be substituted by plastic teeth, enabling more color options and ultimately reducing manufacturing costs.

Whether they are metal or plastic, these stamped “teeth” zippers tend to be really durable and stiff, making them great for heavy-duty coats or leather projects. But they are heavier than coil zippers, and they can be harder to open and close.

In the mid 1960’s, coil zippers began to emerge in commercial use. Coil zippers use a continuous nylon coil to form the teeth, sewn to a textile side tape.  Coil zippers tend to be strong and flexible, and are great for curved openings and small pockets. They also have a “self healing” property, so that if a piece of fabric gets caught in the zipper and bends the teeth, repeated pulling the slider open and closed will actually get the teeth to realign and repair the zipper.

Reverse coil zippers are made with the same continuous nylon coil, but the coil is on the back side of the zipper, and the slider is on the (now) front side of the zipper. Most water-resistant zippers are configured this way, by coating the tape with some kind of rubber, PVC, or TPU coating to achieve water resistance.

Track type water-repellent zippers don’t use teeth or textile at all, they are made entirely from molded TPU, with channels that lock together like a ziplock bag.  Track type zippers are the next generation of waterproof and air-tight zippers. But they are still evolving and developing in terms of durability, flexibility, and reliability.

Water resistant vs waterproof

If you’ve peeked your head into the world of outdoor adventure in the past decade, you’re familiar with the term “Waterproof Zipper.” People use it casually for apparel and bags to describe any zipper that will prevent rain or snow from penetrating under normal use. Technically, waterproof means something that can be fully submerged in water for a long time. What we are really talking about with outdoor apparel and gear is “water resistant”.

Truly waterproof zippers like what you might find on a drysuit for scuba are tested to withstand being submerged for long periods of time. They use a specific double-clasp approach to seal a waterproof textile over the teeth. But they’re bulky and finicky, and even the most adventurous pros aren’t going to be actually submerging their camera bags - well, not intentionally, anyway! 

f-stop Mountain Series packs use water-resistant zippers with Thermoplastic Polyurethane (TPU) coating on each side of the zipper, known as the tape. To build these zippers, the factory first constructs long chains of the zipper, then sends the zipper to a trusted supplier for TPU coating. Once coated, the zippers are quality tested, and then the zipper pull is installed “inside out” compared to the traditional way, maximizing the external surface area of the TPU (we also call this configuration reverse coil). These zippers deliver water-resistant protection similar to the face fabrics used in each pack, and can be sewn or welded to the fabric and taped, just like a seam on a jacket.  Our rule of thumb? If the pack fabric keeps water out, so should the zipper we use for that pack.

Zippers on Mountain Series and Urban Series are tested by our Ambassador team in all conditions.


Weight Considerations

Outdoor gear, whether it is clothing or equipment, needs to be light. And for this reason, most of the zippers you’ll find on outdoor gear are nylon coil zippers. While the size of the zipper affects weight, nylon coil zippers typically weigh up to 80% less than a similarly sized metal toothed zipper, and about half the weight of a plastic toothed zipper. Of course, there are exceptions, but most of the water-resistant packs on the market have reverse coil, water-resistant zippers due to weight and reliability.


A pack that won’t close becomes essentially useless, so zipper strength and durability are critical. Our Mountain Series needs to stand up to the harshest environments on the planet. Tropical rainforests, snowy peaks, desert sun and wind, and rocky crags just to name a few. Our pros depend on the Mountain Series to stand up to years of reaching for a new lens, resting the pack awkwardly on rough surfaces, falling, scraping, and dragging across airports or up staircases. So we overbuild them in every detail. From the laminated fabric to the reinforced handles and straps, to the closures.

Our zippers meet or exceed global standards for water-resistance, puller strength, puller twist strength, zipper lateral strength, and a reciprocation test for f-stop in their internal testing lab.  The global standard for water is ISO-811-2018. f-stop zippers get tested at 60 Mbar/Min water pressure.

f-stop also performs exhaustive tests for the strength of the puller attachment, puller twist strength, the lateral pull-strength of the zipper, and for f-stop, a reciprocation test (thousands of cycles of opening and closing the zippers).

What is the next step in zippers for f-stop?

f-stop currently uses water-repellent, reverse coil zippers on all our packs. But in our quest to continuously innovate our products, we are exploring different zipper choices, and working with suppliers to develop and create new, unique zippers to meet our future needs.  We might use more track-type zippers in our packs, as they become more durable, flexible, and discrete.

Focus on the future

f-stop continues to strive to build the best tools for adventure photographers. We aim to build the most durable, innovative, and comfortable gear bags that our community of ambassadors will love, but always with an eye to reducing our environmental impact. We select every component and material based on this commitment. Whenever possible, we take a few steps closer to this goal. Take a look at any of the Mountain Series packs, and see what makes f-stop the pros’ choice for serious adventure.


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