3c and 4a hair is quite similar. However, 3c hair tends to have an S-shaped curl pattern that ends in an O shape, whereas 4a hair has tiger coils that are more defined than 3c hair. In addition, 4a hair is thicker and coarser in texture than 3c hair and tends to have low porosity than 3c hair. 4a hair is also more prone to shrinkage than 3c hair.