Standard nib dimensions: L 27mm (1.06 inches) x D 1.75mm (0.07 inches), Felt nib dimensions: L 26.8mm (1.06 inches) x D 1.76mm (0.07 inches) Standard nibs are made of durable POM material, high quality and solid. Felt nibs features high-friction for more pencil-like feel. These 2 types replacement nibs are both compatible with Xencelabs 3 button Pen (PH5-A) and thin pen(PH6-A). Not compatible with Xencelabs Pen Display 24. These replacement nibs may also fit the digital pens of other manufacturers.