Description Pilot 0.7mm (BTRF-6F) Ballpoint INK Refills QTY: 3x BLACK 0.7mm Features: * Ballpoint ink refill for PILOT Birdy mini ball pen / Uniball Jetstream 3 & 4, Uniball Jetstream 4+1 multi-pen * Refill length: 9.9cm, Diameter: 3mm , (check your pen and may be suitable for other brand compatible multi-pen) * Oil-based pigment ink, giving it great waterproofness and fade-resistance.