3b with some 3c. 4a is the size of a coffee stirrer straw. 3b is the size of normal size chalk (circumference) and 3c is somewhere between the two. 3c is also known as hair that grows up before it grows down, example, Tia and Tamera Mowry before they began straightening their hair on Sister 2 Sister in early 90s. 4a hair looks more like 3c as i gets more length.
3b/c, medium-coarse, low porosity, high density HG: Jessicurl Too Shea and Kinky Curly Curling Custard Shampoo: nonsulfate shampoo and Suave Naturals sulfate shampoo when needed