A seamless hair extension is a type of clip-on hair extension. The extension hair is called the weft. Near the top of the weft, a metal clip mounted to the weft on a silicone base is used to attach the extension to your natural hair. In a traditional clip-on extension, the base that attaches the metal clip to the weft is fabric.
People may prefer seamless extensions due to their lower profile; the silicone can be up to 50 percent thinner than the fabric, making the extension appear more natural — and, therefore, seamless. Seamless extensions usually can be washed (although you shouldn’t keep them submerged for more than 20 seconds) and heat-styled on lower heat settings. You can gently brush seamless hair extensions as well as have them dyed a darker color by a trained professional.