A hair extension is a beauty product designed to give you the appearance of longer and/or fuller hair. Hair extensions are made of synthetic material or real human hair and are attached to your natural hair by a variety of techniques such as a weave (sewing), hot fusion, tape-in, cold fusion, bonding, metal clips, micro ring or micro loops, and more. The type of technique you select as well as the quality and volume of the hair you choose all affect cost. Hair extensions can last anywhere from three weeks to six months, depending on the application technique. For example, tape-in extensions may last approximately four weeks, while extensions applied using a hot fusion technique may stay in for up to six months. The hot fusion technique takes longer, costs more, and requires more training on the part of the hair stylist, but the result is more natural-looking extensions that can be washed and heat-styled with confidence.