The accepted threshold hail size that is believed to be responsible to damage of vehicles is basically 2cm. Dents from hailstones of this size are usually difficult to recognise except for those specialising in hail dent repair and removal.
As hailstones increase in size, the impact of both the mass of the hailstones, the hardness and sharpness of the hailstones, and the angle of impact all contribute to the extent and severity of damage to vehicles and of course buildings. Countless case studies and impact experiments have been used to measure the correlation between hail size and impact damage.
The Dent Shed.
This very organised company of experienced professionals has a location near you so please for further information.