The Pilot G-TEC-C4 Gel Pen Refill 0.4mm Black (BLS-GC4-B) is a genuine Pilot replacement refill designed for compatible Pilot G-TEC-C4 gel pens. Filled with rich black bio-polymer gel ink, it delivers exceptionally smooth, precise, and skip-free writing through its ultra-fine 0.4mm tip. Perfect for technical drawing, detailed writing, document preparation, journaling, planners, and professional use, this genuine Pilot refill restores your pen's original writing performance while extending its lifespan.