FI2307: The 20L Submersible Backpack and IPX7 Versus IPX4 in One Bag

A backpack sold as submersible has one question to answer before any other: which part of it is submersible? On the FI2307 the answer is exact, and it is not the whole bag. The main compartment closes on an IPX7 waterproof zipper. The front pocket closes on an IPX4 water-resistant zipper. Those two closures sit a few centimetres apart on the same face, and they promise two different levels of protection. A listing that averages them into "IPX7 backpack" is making a claim the product cannot support, and it is the kind of claim that comes back as a refund after the first river crossing.

That split is why this bag deserves a technical read rather than a paragraph of feature copy. Most 20 L daypacks in the fishing and outdoor category use either a roll top or a flap-covered zip, and both ask the buyer to accept one vague promise for the whole bag. FI2307 separates a dry core from a splash-resistant outer pocket. That is a more honest arrangement, and a harder one to merchandise, because the person writing the product page has to keep two ratings separate all the way through the copy.

The bag is also a useful case study in material choice, because the same product family is built two ways: 1680D PVC fabric on the FI2307, and 840D nylon with double TPU on the three sibling models. Neither route is better in the abstract. They fail differently, they age differently, and they ask different things of the factory.

The FI2307 on the data sheet

The published specification is deliberately short. Shell: 1680D PVC fabric. Weight: 1.34 KG. Volume: 20 L, in a body measuring 51 x 28.5 x 14.5 cm. Colours: Black and Green. Closures: IPX7 waterproof zipper on the main compartment, IPX4 water-resistant zipper on the front pocket. Intended use: fishing and outdoor.

The geometry is worth reading before the materials, because 51 x 28.5 x 14.5 cm already tells you what kind of object this is. A 28.5 cm wide body only 14.5 cm deep is a panel, not a barrel. It hangs flat against the back, it does not roll sideways when it is half full, and it fits into the space between a boat seat and a gunwale that a rounder pack cannot use. The 51 cm height is what gives 20 L without depth: the volume is stacked vertically, which keeps the centre of gravity high but close to the spine.

The first discrepancy a buyer will notice sits inside the product imagery itself. The dimension panel prints 1680D polyester in its fabric row, while the product data names 1680D PVC fabric. Both refer to the same 1680D yarn size, but one describes a base cloth and the other describes a coated polymer, and a listing that mixes the two will eventually be quoted back by a customer who reads labels. Treat the fabric line as a question to close with the supplier in writing, not as a phrase to copy from a picture.

Two IP ratings on one bag, and why that is deliberate

The second digit of an IP rating describes water, and the numbers are not a scale of quality. IPX4 is a splash test: water thrown at the enclosure from any direction must not cause harm. IPX7 is an immersion test: the enclosure is submerged under defined conditions and checked afterwards. Between the two there is a change of physical principle, not a step up a ladder. A splash-rated closure can shed rain all day and still fail the moment it goes under; an immersion-rated closure can survive a dunking and still be the wrong choice for a pocket you open many times a day.

That is the trade the FI2307 makes, and it is a sensible one once you look at how the bag is used. The main compartment holds the things that must not get wet: a camera, a spare layer, documents, a phone. It is opened at the start of the day, at lunch, and at the end, and it can afford a stiff closure that takes two hands and a deliberate pull. The front pocket holds what a wading angler reaches for constantly: leader spools, pliers, tippet, a snack. An airtight zipper there would be slower, stiffer and more expensive, and every opening would wear the seal. So the design puts the slow, high-sealing closure where the consequences of failure are worst, and the fast, lightly sealed closure where speed matters.

Two consequences follow for anyone selling or specifying the bag. The first is copy discipline: the main compartment is submersible to IPX7, the front pocket is splash resistant to IPX4, and the body, back panel, shoulder straps, webbing and mesh side pocket carry no rating at all. The second is user training. A buyer who does not know which pocket is which will put a phone in the front pocket, wade to the chest, and then blame the product. A hangtag diagram costs almost nothing and prevents that return.

1680D PVC versus 840D nylon with double TPU

The FI2307 is built on 1680D PVC fabric. The 906-001, 906-008 and 906-010 in the same family are built on 840D nylon with double TPU. Reading those two lines correctly is most of the material decision.

Start with what the words do and do not say. 1680D is a yarn size in denier, a coarse yarn, and it tells you the face cloth is built from heavy filaments. PVC names the polymer, not the construction: a PVC-coated fabric can be coated on one side or both, and the coating weight is a separate number that this data sheet does not publish. Double TPU on the nylon models says the composite carries two TPU layers, which is a construction statement, not a thickness. None of these strings gives a fabric weight per square metre, a coating thickness, a peel strength, an abrasion cycle count or a cold-flex temperature. Any of those figures has to come from the supplier in writing, and none should be inferred from the yarn count.

What can be said without inventing numbers is how the two routes behave, because that follows from the structure rather than from a test. A PVC-coated 1680D face is heavier and stiffer per unit area. Stiffness is an asset on a panel-built bag: the front face holds its shape, the bag stands up when it is set down on a wet deck, abrasion from rock, gunwale and boat floor is spread over a hard surface, and fish slime and bait wash off with fresh water. The same stiffness is a liability in the hand. PVC panels feel boardy in cold weather, creases tend to stay where they are put, and a bag that will not fold flat takes up space in a vehicle or a pack.

The 840D nylon with double TPU route trades that stiffness for compliance. The composite drapes, follows the shape of the load, conforms to the back instead of standing off it, and folds flat when empty. That is why the roll-top 906-008 can be compressed down as its contents shrink, and why the 906-010 works as a body-fit hip pack. The cost is that a soft face transmits abrasion and impact to the laminate beneath it more directly, and a soft bag does not stand up on its own.

Process follows material. PVC is a weldable polymer, so a factory can join panels by high-frequency welding or heat sealing rather than by stitching alone, which removes needle holes from the seam line. Composite nylon is normally sewn and then sealed at the seam with tape. Neither method is automatically drier: what matters is whether the seam treatment is specified, inspected and tested, and whether the supplier can document it. For the FI2307, ask which seams are welded, which are sewn, and how the sewn ones are sealed.

There is a third variable that matters for anyone selling into a cold market, and it is the one least likely to be documented. Low-temperature behaviour of a PVC coating and of a TPU laminate is not the same, and the difference shows up as stiffness, cracking at fold lines and delamination after a season of cold storage. No low-temperature figure is published for either material in this family. Ask for it, in writing, before a winter programme is committed.

20 L and 1.34 KG: a wading daypack, not a hiking pack

Divide volume by weight and the FI2307 looks heavy: 1.34 KG empty for 20 L of space. That ratio is not a defect, it is a description. The mass sits in the closure system and the shell, and both exist to keep water out rather than to carry a sleeping bag. Read the number as a positioning statement: this is a bag for the wet part of a day, not for distance.

A 20 L body is a specific carrying capacity, and it is easier to plan against a list than against a volume figure.

That list fills the bag. What it does not include is the reason to be honest with end users: there is no room for a sleeping bag, a stove, a tent or several days of food, and a 20 L pack loaded for an overnight trip stops being a dry bag because the zip can no longer be closed over the load. A zipper that will not seat at the end stop is an open door. Capacity claims and IP ratings are linked, and the link is the closure.

The carry system is built for the same short-haul use. A molded back panel with a foam shoulder strap assembly, a chest belt and a hip belt will hold a light load steady while wading or climbing in and out of a boat, which is exactly the moment a pack shifts and puts you off balance. It is not a load-carrying harness for an expedition load, and it does not need to be.

Where the FI2307 sits in the line

The family is easier to sell when the four models are presented as four jobs rather than four sizes.

Two readings stand out. The 906-001 carries both compartments at IPX7 in 37 L at almost the same weight as the FI2307, which tells you that the extra volume comes from the lighter composite shell and that the difference between the two bags is structure, not sealing ambition. And the 906-010 shows that a 9 L hip pack can hold an IPX7 main compartment, so IPX7 on a small body is a design choice rather than a physical limit.

The FI2307's own case is the split rating plus the PVC panel. If a programme needs one bag that survives being set down on a wet deck, wiped clean and loaded against a hard frame, the PVC panel is the argument. If it needs a bag that packs into a duffel and disappears when empty, the 25 L roll top is the argument. Both are in the same catalogue, and neither needs to be described as the other.

IP ratings are test conditions, not guarantees

An IP rating describes how a sample performed under a defined test. It does not describe how the bag on a customer's back will perform in its third season, and the gap between those two things is where most water-damage complaints are born.

The failure modes are ordinary and predictable. A zipper that is closed but not seated at the end stop leaves a gap the width of the slider. Sand, grit and salt crystals in the teeth hold the seal faces apart and abrade them every time the slider passes. A seal face that has dried out, hardened or been nicked in storage no longer meets its opposite face evenly. A bag that is packed so full the zip is under tension will not seal along its length, and a bag dropped on a hard corner can deform the closure track. None of these is a manufacturing defect, and all of them look like one from the customer's side.

The maintenance routine that follows is short and worth printing on the care label. Rinse the bag with fresh water after saltwater use and dry it fully open, because salt left in the teeth is abrasive. Close the air valve before any immersion, and open it when the bag is stored so the shell is not held under pressure. Never clean the closure with a high-pressure washer, which drives water past the very seal the bag is built around. Avoid long exposure to direct sun, which ages a PVC coating faster than use does. Store the bag unzipped and unstressed so the seal faces are not compressed for months. Check the seal face for grit and nicks before every trip, and use only the lubricant the supplier specifies, if any.

For the front pocket the standard is lower by design. IPX4 means splash, so rain, spray and a wet hand are inside the specification and a dropped bag in the bottom of a boat is not. That is not a weakness in the product; it is a weakness in any listing that lets the buyer assume otherwise.

A buying and inspection checklist

The gaps in the published data are the agenda for the first supplier conversation. Each line below is either published, or it has to be confirmed in writing before a purchase order is raised.

Two practical notes on running those checks. First, an immersion test is only meaningful if the pass criteria are written down before the test: which compartment, how much air is left in the bag, whether the bag is weighted, and what counts as ingress. Second, sample the seal face with a fingertip and a torch on every incoming lot. It costs seconds per bag and catches the two failures that matter most, grit contamination and a nicked sealing edge.

FAQ

Is the whole FI2307 rated IPX7?

No. The main compartment closes on an IPX7 waterproof zipper. The front pocket closes on an IPX4 water-resistant zipper. The body, back panel, shoulder straps, webbing and mesh side pocket carry no IP rating. Any listing that describes the complete bag as IPX7 is inaccurate.

Can the bag be submerged?

The main compartment is built for short-term immersion, and that is the only part of the bag the rating covers. Submersion is only valid with the closure fully seated, the seal faces clean and the air valve closed. The front pocket should be treated as splash resistant and nothing more.

Is 20 L enough for a day of fishing?

For a wading or boat day, yes: camera and one lens, a spare layer, phone and documents in the main compartment, terminal tackle and tools in the front pocket, a bottle in the side pocket. It is not enough for an overnight trip, and overloading it until the zip will not seat defeats the point of the bag.

Why is a 20 L pack 1.34 KG?

The weight is in the closure system and the 1680D PVC shell. An airtight zipper, a stiff panel-built body and a molded back panel all add mass that a lighter roll-top bag does not carry. The trade is protection and structure against weight.

How does it differ from the 906-001?

The 906-001 is 37 L in 840D nylon with double TPU at 1.35 KG, with both main and front compartments at IPX7 and a front webbing panel with detachable compression straps. The FI2307 is 20 L in 1680D PVC at 1.34 KG with a split IPX7 and IPX4 rating. One is a larger, softer, fully sealed bag; the other is a smaller, stiffer, structured daypack.

Can a rod be carried outside the bag?

The imagery shows a removable fishing rod holder on the front face, which keeps a wet rod outside the dry compartment. Confirm the holder's fixation method and load limit with the supplier, since neither is documented in the published data.

The FI2307 is best understood as a bag with a dry core and a wet-access shell, and every useful statement about it follows from that. The main compartment is the part that crosses the river. The front pocket is the part that gets opened with wet hands. The 1680D PVC panel is what lets the bag be set down on a deck and wiped clean afterwards, and it is also what makes it heavier and stiffer than its nylon siblings.

For a buyer, the work is in three places. Keep the two ratings separate in every line of copy, and never let a marketplace template collapse them into one. Close the unpublished numbers in writing: coating thickness, coating passes, seal face width, seam treatment, cold-fold behaviour and the immersion pass criteria. And match the bag to the job, because a 20 L panel pack that holds a camera, a layer and a day of terminal tackle is a different product from a 37 L soft bag that swallows a weekend.

Get those three right and the listing survives the first customer who actually wades with it, which is the only test that counts.