In these kinds of hair, the hair is sewn on a special sewing machine creating a string like weft of hair that is generally very strong. The hair is sewn once and then it is folded over and sewn again so that the hair does not slide out of the seam. Only the people with thin hair might find it difficult to carry them. Using special keratin glue, the hair can be easily glued in. They do not damage hair and can be easily removed by using either oil or solvent.
This category consists of small strands of hair woven into a few strands of finishing line. Expensive than machine weft it is much thinner, more unified and also less likely to shed. They are usually made to a specific length needed and are best applied with any sew-in method.