How to Choose a Watertight Case: Size It From Your Equipment, Not From the Catalogue

Most people choose a watertight case the wrong way round. They open a catalogue, pick the size that looks about right, then discover at the airport that the lid will not close over the lens hood — or that the case is 8 cm too short for the tripod.

The reliable method runs the other direction. Start with a list of what has to travel, turn that list into a cavity, and only then look at models. It takes about fifteen minutes and it eliminates the single most common buying mistake.

Step 1 — Inventory the kit, including the things you forget

Write down everything that goes in the case, not just the headline items. The headline items are the ones you remember; the accessories are the ones that force you into a bigger box later.

For a camera kit that means bodies, lenses, and also batteries, chargers, cards, filters, a cage, cables, and the L-bracket you keep meaning to remove. For a drone kit it means the airframe, controller, batteries, charger hub, spare props and a landing pad. For test equipment it means the instrument, probes, power supply, manuals and calibration certificate.

Two columns are worth filling in: must go in the case and can travel separately. That second column is where you save money — a charger that lives in a backpack does not need 3 litres of foam.

Step 2 — Measure three dimensions, and one you did not know about

You need the longest, widest and tallest items. Measure them as they will be packed, with hoods reversed, handles folded, cages fitted.

Then check depth splits, because this is the specification most buyers never read. A watertight case is not one open box; it is a lid plus a base, and the split matters:

Total depth tells you the overall cavity.

Bottom depth tells you what can stand upright.

Lid depth is usually shallow — 47 mm on the 443419, 50 mm on the 1303214, 55 mm on the 584433.

A tall item must fit inside the bottom depth plus whatever foam you remove — not the total depth. A 190 mm total depth with a 47 mm lid is really a 143 mm base with a thin lid cavity on top. Buy on the total figure alone and a tall body will not close.

Step 3 — Leave room for foam to compress

Foam is not decoration. It is the part that decouples your equipment from the shell, and it only works if it is slightly compressed when the lid shuts.

That means the cavity you need is larger than the kit you measured. Plan a margin around each item rather than a perfect fit, and think in layers: cases in this range ship with three or four layers of PU foam, and you cut or pluck down through them to the depth your equipment needs.

If you are buying a case with pre-cut foam, the layout is fixed — great value, but only if your kit matches it. If you are buying pick-and-pluck, you shape it yourself, and a mistake costs you a layer. If you are buying empty, you supply your own divider set or insert.

Step 4 — Choose the format before the dimensions

Format follows from how the case moves, and weight decides more of this than volume.

Hand-carry. Fine up to roughly 15 kg loaded. Beyond that you will start leaving the case in the van, which defeats the point. The 443419 at 4.9 kg with foam is a hand-carry case.

Wheeled. Once the loaded weight passes that threshold, two casters and a handle stop being a luxury. The 584433 runs 10.92 kg with foam at 84.3 litres; the 1303214 runs 8.4 kg at 55.84 litres. Both are built around being rolled, not lifted.

Long. Tripods, light stands, boom arms, rods and long instruments break the normal aspect ratio. The 1303214 is 1308 mm internally and takes items up to about 50 inches — a format decision, not a size decision.

Flat. Laptops, tablets, panels and flat instruments want depth measured in centimetres, not tens of centimetres. The 322505 is 43 mm internal at IP65. Do not buy a deep box for a flat object and fill the rest with foam.

Step 5 — Match the measurement to a cavity

All dimensions below are internal, verified against current product specifications.

Read the table as a filter, not a ranking. The 584433 holds twice what the 443419 holds, but it also weighs more than twice as much empty — 9.65 kg against 4.45 kg. If you only ever move it between a car and a stage, that is fine. If you carry it up stairs, it is not.

Foam, dividers, or nothing

There is no universally correct interior. Match it to how often the kit changes.

Fixed kit → pre-cut or pick-and-pluck foam. Each item gets a home. Nothing shifts, nothing rubs.

Changing kit → dividers. The 443419 is built around a custom divider insert precisely because gear evolves; the insert can be reconfigured when a lens is replaced.

Shared case → empty shell plus your own insert. Common when one case serves different jobs across a week.

A practical warning: foam holds moisture against equipment. If a case comes in wet from a job, open it, remove the foam if it is soaked, and let everything dry before closing it again. A watertight case will happily preserve a damp environment for weeks.

What “watertight” should actually mean

Two things are worth checking on any spec sheet, and neither is the word “waterproof”.

The IP rating. IP67 means dust-tight and protected against temporary immersion — 1 metre for 30 minutes. IP65, as on the 322505, means dust-tight and protected against water jets: rain and spray, but not submersion. Both are legitimate; they answer different questions.

The seal as a wear item. A rubber O-ring running the perimeter is what makes the rating real, and it is the first thing to degrade. Sand, salt crystals and a folded cable can all defeat a seal that passed inspection last month. Wipe it, inspect it, and keep the mating surface clean.

A pressure equalisation valve belongs in the same conversation: it lets the case equalise after an altitude change without breaking the seal, which is why a case that sealed at sea level still opens at 2,000 metres.

Four questions worth answering before you pay

1. What is the single largest item, measured as packed? That sets the case. Everything else arranges around it.

2. How far do you actually carry it? Distance, not volume, decides whether you need wheels.

3. Will the kit change in the next year? If yes, buy the interior that can change with it.

4. How often do you need to get into it? A case you open ten times a day should be easy to open with one hand.

FAQ

Can I use the external dimensions to judge capacity?

No. External figures include walls, ribs and hardware. Always size from internal dimensions, and from bottom depth for anything tall.

Is IP67 enough for a boat or a wet deck?

For transport, yes — rain, spray and a temporary dunking are covered. It is not a substitute for a waterproof housing if the equipment itself goes underwater.

How much heavier is a wheeled case?

Compare empty weights: 4.45 kg for the 443419 against 9.65 kg for the 584433. Wheels add mass, but they remove the reason you would otherwise leave the case behind.

Can you cut foam to my exact layout?

Yes. Custom inserts are available across the range, with samples typically around two weeks. Send a layout with dimensions rather than a photo if you can — it removes a round of guessing.

The right case is the one you stop thinking about

Tsunami has built waterproof, impact-resistant protective cases for over 17 years, from a factory of more than 55,000 m² running 38 injection-moulding machines, over 1,800 mould sets and capacity above 1,200,000 pieces per month — ISO9001-certified, with 74 patents behind the hardware.

Browse waterproof protective hard cases or wheeled hard cases, then send us your kit list — longest item, tallest item, loaded weight — and we will tell you which cavity fits before you buy.