Hair building fibres are the perfect way to add thickness to your hair in just 30 seconds. 100% natural keratin, a fibrous protein found in hair strands. Berkowits hair building merges perfectly with your own hair using electrostatic charge to give instant, natural and durable hair thickness which lasts all day. We're so confident you'll have a great experience with our hair thickening fiber. Key features: instant natural looking. Made from 100% natural keratin. With kinetic technology, fibres bind 400% stronger than others. Available in black and dark brown featuring color lock technology.