Every accessory listing on the internet ends with two letters and a number, and buyers consistently over-read it. "IP67" is not a promise that the product is waterproof. It is a description of a specific laboratory test, and the gap between the test and the promise is where returns come from. Here is what the ratings mean, what they leave out, and what to specify for real-world use.

The first digit is solids, the second is liquids

In an IP code, the first character rates protection against solid objects and the second against water. A rating of IP67 means: protected against solid objects up to 1 mm, and protected against temporary immersion in water to a depth of 1 metre for 30 minutes. IP65 means dust-tight with protection against water jets. IP54 means limited dust ingress and protection against splashing water from any direction. Read the two digits separately — a product can be excellent against dust and poor against water, and a single marketing phrase hides that.

What IP rating does not tell you

Three things. First, the test is on a pristine sample: a housing that passes IP67 can still leak once the seal is damaged by a UV-cracked gasket, a dropped housing or an improperly torqued gland. Second, the rating applies to the enclosure as tested, not to the assembled product — a IP67 cable entering a non-rated enclosure is a non-rated installation. Third, it says nothing about chemical attack, salt, vibration or UV, all of which matter more than immersion depth in a marine or rooftop application.

Match the rating to the application, not to the marketing

For an indoor or sheltered install, IP54 or even a plain indoor rating is fine. For a vehicle roof, an eaves-mounted unit or an outdoor cabinet you will actually maintain, IP65 with a UV-stabilised housing is the sensible minimum. For a marine or coastal application, treat the IP rating as the entry requirement and then add what the rating does not cover: a documented salt-spray result, a UV-stabilised polymer or anodised aluminium, and stainless fixings of the correct grade. Any supplier that can only offer a number and no report is selling you a number.

Other markings worth reading

Alongside IP, look for a temperature range, a salt-spray test standard with hours stated, and a materials declaration for anything that touches skin or food. Marine-grade 316 stainless and 6061 aluminium with a marine powder coat are meaningful specifications; "weather-resistant" is not. For vehicle products, look for vibration and mechanical-cycle ratings, because a mount that passes IP67 and fails a hundred thousand vibration cycles is not a marine product either — it is a marine product with a short life.

Ask for the report, and check the model number on it

The simplest due diligence in this whole category: ask for the test report, then check that the model number printed on the report is the model number on the invoice. Reports are routinely reused across product families. A genuine supplier will send the report within the hour and will not be bothered by the question. PLZTECH publishes the salt-spray and ingress documentation per product and includes it in the shipment file, so you can pass the same evidence to your own customers and to marketplace compliance teams who ask.

One practical rule

Buy the ingress rating that your harshest environment needs, and then buy the enclosure quality that the rating cannot describe. The rating is table stakes; the finish, the gasket and the fastener grade are what determine whether the product is still working in year three.