U Tip Keratin Human Hair Extensions Natural Color #NC | HairperfectoU Tip hair extensions are one of the most popular techniques to use for semi permanent extension applications. U tip Nail tip extensions are pre bonded together with keratin. The bonds are softened with a heating tool called a fusion iron and then bonded to the natural hair. The name 'pre bonded' is derived from the 'pre tipped' keratin bond at the top of each strand. We use high quality virgin human hair to make these best keratin bond hair