Hailstones form in the cold tops of thunderstorm clouds and fall to earth when they move outside the wind flows within a  storm cloud or when they become too large to be supported by the air movements in the cloud. Large hail stones are defined as those that are bigger than 2cm in diameter. Large hail is particularly common in southeast Australia.

The most likely building component to be damaged by hail is the roof covering. Hailstones can cause indentation, puncture or fracturing and the roof covering may need replacement. Although less common, hailstones can also damage windows, external wall coverings and any other exposed surfaces. 

What is the difference between this rating and supplier ratings?

The rating you see at the top of the page is the resilience rating of the generic class of building material to a particular hazard. A supplier rating is particular to a specific supplier product. For example, clay bricks may have a resilience rating of '3' to inundation but a supplier may have made specific improvements to their bricks and may be able to achieve a resilience rating of '5' for their clay brick. "