Benefit Brow Microfill Pen creates the illusion of natural brow hair with 3 ultra-fine lines in a single stroke. It's designed to blend in with existing hairs, fill in gaps and make brows appear where before there were none. The easy-to-apply formula of this brow pen looks natural and is waterproof, smudge-proof and longwearing, creating a microblade effect that lasts for 24 hours.