A 12-inch hair extension is a strip of hair that is 12 inches in length, attached to a person's natural hair. The hair extensions can either be real human hair or synthetic hair.
There are three main methods of applying extensions: fusion, tape-in and weave. Fusion extensions use individual keratin-tipped strands that meld with a person's natural hair using heat. This process takes longer and costs more, but it also lasts the longest. Tape-in extensions simply tape the extensions to a person's natural hair using two-sided tape. It's the least expensive and only takes about an hour, but it doesn't last long. Weave extensions are sewn into a person's natural hair. This method requires strong hair for it to stick, and is not recommended for those with fine or brittle hair.