Uni-ball Jetstream Extra Fine Point Roller Ball Pens Refills for Multi Pen Type-0.5mm-blue Ink-value Set of 5 Extra Fine Point-0.5mm- Writes amazingly smooth while providing crisp, vivid lines Quick-drying ink helps prevent smearing - perfect for left-handed writers Conformity number/SXE3-400/MSXE-500/SXE3-601/MSXE3-701/MSXE-1000 Keep in mind that it does not fit normal Jet Stream.