They are individual extensions made of a synthetic material to look like ideal natural eyelashes; thicker at the base and thinner at the tip with a slight curl. They are attached semi-permanently one by one to a natural lash with a medical-grade bonding adhesive giving the appearance of a darker, more attractive lash-line. Typically, eyelid has approximately 100 natural hairs which shed at an average rate of 20-30% every 2 weeks. Therefore, the natural eyelash sheds with the extension that was attached to it. Since new eyelashes are always growing, refills can be performed to adhere extensions to the new growth keeping the lashes looking their best for as long as you wish to maintain them.