The difference is only the weight. All of our extensions are made of the same high quality grade 100% Remy Human Hair. If your hair is fine to medium and/or you are looking for length and some volume then our 120 grams set is more suitable for you, this amount of hair is suited to finer hair as it will certainly be all the hair you need to get your desired volume & length. If, however, your hair is thick or you are looking for lots volume as well as length we recommend our 160 grams set, which provides even more hair. It will blend in with naturally thick hair and create lots of volume for all hair types.