Silk Strong Hold Lash Bond Liner usesBidirectional Film Forming Technologyto create the ultimate hold for false lashes. This film-forming agent is known as a PSA (pressure sensitive adhesive). Pressure Sensitive Adhesives are a type of non-reactive adhesive which form a bond when light pressure is applied with a surface. PSAs also display elastic properties which enable re-sticking! This functionality allows you to re-apply or adjust your lash if you first apply it incorrectly. This revolutionary and remarkable film-forming capacity toward both surfaces ensures a unique and reliable bond between the liner and lashes.