Human Hair Structure (the cuticle)
Hair is made of different layers. The outer layer, called the "cuticle", is made up of overlapping layers of long cells. They lie on the surface aligned in the same direction like the tiles on a roof with their free edges directed towards the tip. The cuticle locks in essential moisture and protects the hair against outside elements. A healthy cuticle is much more than just a protective layer. Much of the shine is due to the cuticle, light reflects from their glossy surfaces. This, together with the pigment within the cortex, gives hair its characteristic appearance. Hair without cuticle would appear dull and lifeless, it would dry out and become brittle.

Human hair extensions

The human hair used in the hair extension industry comes in different qualities. In general we can say that we get what we pay for, the lower the price of your hair extension the less hair quality we can expect. The highest quality hair will still have all it's cuticle perfectly aligned in the same direction. If the cuticle scales are not facing the same direction, hair will interlock like Velcro, this will lead to matted and tangled hair.
Cheaper hair is very often placed in an acid bath which completely destroys the cuticle. To restore the shine this hair is covered with a silicon layer. It looks beautiful but after a few washes the silicon is removed and the hair mats, tangles, and becomes dry.

European human hair does not necessarily come from Europe. It is a group name for different hair with an almost similar structure. Indian hair, Latin American hair, European hair, the only exemptions are Asian hair and African hair (their structure is very different).
Typical European human hair is relatively thin and has an oval cross-section.
This is a popular hair type for a human hair extension.

Asian hair (mostly Chinese hair) is very often used for human hair extensions. This hair is thicker than European hair and has a round cross-section. It is dark black.
To prepare this hair for use in hair extensions it is usually made thinner (acid bath) and lighter. This hair is less expensive.

Indian hair has a very similar basic structure as European hair. In general this hair type is of a very high quality. However the method of collection is very essential. When different types of hair are mixed with cuticles aligned in different directions this hair becomes of a much less quality and therefore less expensive. To prevent tangling the cuticles must be removed and the hair is covered by silicon. Hair companies in Korea and Indonesia are specialized in this type of hair.
Collected in the right way with all the cuticles present and in the same direction this hair is one of the best hair types available for use in a human hair extension.

Remi hair is a name you will hear when you shop around for hair extensions. They claim to use only the finest and most beautiful human hair in the world with all cuticles in the same direction.

Synthetic hair is man-made fiber that is made to look like your own hair. It produces a different sheen than human hair, moves differently and therefore does not blend with human hair. New fibers are developed continuously that are better resistant to heat and have an appearance closer to human hair. It comes in a large variety of colors. This hair is the most inexpensive. Sometimes this hair is mixed with human hair and a combination is used for a human hair extension. In most cases this is of course not the way to do it. Both hair types need a different after care.

The majority of hair sold today is non-cuticle hair, which is less expensive. So if you want to spend less money on your hair extension this could be fine for you as long as you realize that this hair will probably start matting, tangling and become dry a lot sooner than a higher quality hair.

Overheating is one of your hair's biggest enemies, the damage can be as deep as the cortex which is in the middle. Be careful not to use too much heat when you use a blow dryer or curling iron. It is best to let your hair dry naturally.
Chemical treatments like color and perm can be harmful as well. Go to your stylist for advise, they should know what is best for your hair. Brush your hair gentle to prevent damage. This is not just better for your hair extensions but it will also keep your own hair healthier.

European and Indian Remi hair is the most popular for a human hair extension but also the most expensive.

Courtesy of: http://www.hairextensionguide.com/hair.htm