The waterproof performance grade of sunglasses

The waterproof performance grades of sunglasses are usually classified from 0 to 5 according to the general standards in the industry:

Grade 0: Completely non-waterproof and will be damaged upon contact with water.
Grade 1: Slightly waterproof. A small amount of water splashes onto the temple of the lens may not cause significant damage, but prolonged contact with water or excessive water splashes can cause problems.
Grade 2: Medium water resistance, capable of withstanding a certain amount of water splashes and short-term contact with water, but not suitable for prolonged immersion.
Level 3: Good water resistance, capable of withstanding considerable water splashes and short-term immersion. Water contact during daily use is basically unaffected.
Grade 4: Excellent waterproofing, capable of withstanding heavy water splashes, rain erosion, and prolonged immersion.
Grade 5: Top-notch water resistance, it can be used normally in almost any water environment.
In actual tests, waterproof performance is usually evaluated by simulating water splashes that may be encountered in daily activities. For example, use a spray bottle to spray water on the surface of the temple at a uniform speed. After a period of time, observe the adhesion and penetration of water droplets on the surface of the temple. In addition, the performance of the temple legs after prolonged contact with water can also be evaluated through immersion tests, such as observing whether there is any deformation, fading, peeling or other phenomena on the surface of the temple legs, as well as whether the internal structure is affected.