HP Pigment 5X100ML Refill ink kit for 950 950XL 951 951XL Officejet Pro 8100 & 8600 High quality refill pigment ink Particles: &lt;0.5 micron (Average&lt;100 nanometer); Stability: No settling in 2 years (at normal storage); Lightfastness: 7-8 BWS; Rubfastness: 5 (Excellent); Waterfastness: 5 (Excellent); Gasfastness: 5 (Excellent).