There are several different types of extensions that each come with a different number of strands. Here is a list of the different packs:
There are 20 strands in each full pack that make 10 complete extensions.
Mini Packs and Fantasy Packs contain 12 strands that make 6 complete extensions.
Rainbow Packs contain 24 strands that make 12 complete extensions.
Micro Strands come in 20 Piece Packs.