What are the different hair length numbers used in the hairdressing industry and how do they correspond to specific lengths of hair?

In the hairdressing industry, different hair length numbers are used to indicate specific lengths of hair. These numbers typically range from 1 to 8, with 1 being the shortest and 8 being the longest. Each number corresponds to a specific length of hair, with shorter numbers indicating shorter lengths and longer numbers indicating longer lengths. Hairdressers use these numbers as a reference when cutting or styling hair to achieve the desired length.