We usually recommend these amounts for a full head, length plus thickness:
(Note: for 24" length, go with the higher density to allow for shedding)
Thin hair: 120-140g
Med. hair: 160-180g
Thick hair: 180-220g
If installing very long hair (24"), you will need a minimum of 100g on the bottom row in order to maintain thickness at bottom, otherwise it will look thin and stringy.
